"fatal" was meant as "we need fatal for the connection, it will be dropped".
but it sounds more serious, as if something needs to be fixed.
hopefully enough for issue #39 by ArnoSen
in smtpserver, we store dmarc evaluations (under the right conditions).
in dmarcdb, we periodically (hourly) send dmarc reports if there are
evaluations. for failed deliveries, we deliver the dsn quietly to a submailbox
of the postmaster mailbox.
this is on by default, but can be disabled in mox.conf.
with requiretls, the tls verification mode/rules for email deliveries can be
changed by the sender/submitter. in two ways:
1. "requiretls" smtp extension to always enforce verified tls (with mta-sts or
dnssec+dane), along the entire delivery path until delivery into the final
destination mailbox (so entire transport is verified-tls-protected).
2. "tls-required: no" message header, to ignore any tls and tls verification
errors even if the recipient domain has a policy that requires tls verification
(mta-sts and/or dnssec+dane), allowing delivery of non-sensitive messages in
case of misconfiguration/interoperability issues (at least useful for sending
tls reports).
we enable requiretls by default (only when tls is active), for smtp and
submission. it can be disabled through the config.
for each delivery attempt, we now store (per recipient domain, in the account
of the sender) whether the smtp server supports starttls and requiretls. this
support is shown (after having sent a first message) in the webmail when
sending a message (the previous 3 bars under the address input field are now 5
bars, the first for starttls support, the last for requiretls support). when
all recipient domains for a message are known to implement requiretls,
requiretls is automatically selected for sending (instead of "default" tls
behaviour). users can also select the "fallback to insecure" to add the
"tls-required: no" header.
new metrics are added for insight into requiretls errors and (some, not yet
all) cases where tls-required-no ignored a tls/verification error.
the admin can change the requiretls status for messages in the queue. so with
default delivery attempts, when verified tls is required by failing, an admin
could potentially change the field to "tls-required: no"-behaviour.
messages received (over smtp) with the requiretls option, get a comment added
to their Received header line, just before "id", after "with".
getting mox to compile required changing code in only a few places where
package "syscall" was used: for accessing file access times and for umask
handling. an open problem is how to start a process as an unprivileged user on
windows. that's why "mox serve" isn't implemented yet. and just finding a way
to implement it now may not be good enough in the near future: we may want to
starting using a more complete privilege separation approach, with a process
handling sensitive tasks (handling private keys, authentication), where we may
want to pass file descriptors between processes. how would that work on
windows?
anyway, getting mox to compile for windows doesn't mean it works properly on
windows. the largest issue: mox would normally open a file, rename or remove
it, and finally close it. this happens during message delivery. that doesn't
work on windows, the rename/remove would fail because the file is still open.
so this commit swaps many "remove" and "close" calls. renames are a longer
story: message delivery had two ways to deliver: with "consuming" the
(temporary) message file (which would rename it to its final destination), and
without consuming (by hardlinking the file, falling back to copying). the last
delivery to a recipient of a message (and the only one in the common case of a
single recipient) would consume the message, and the earlier recipients would
not. during delivery, the already open message file was used, to parse the
message. we still want to use that open message file, and the caller now stays
responsible for closing it, but we no longer try to rename (consume) the file.
we always hardlink (or copy) during delivery (this works on windows), and the
caller is responsible for closing and removing (in that order) the original
temporary file. this does cost one syscall more. but it makes the delivery code
(responsibilities) a bit simpler.
there is one more obvious issue: the file system path separator. mox already
used the "filepath" package to join paths in many places, but not everywhere.
and it still used strings with slashes for local file access. with this commit,
the code now uses filepath.FromSlash for path strings with slashes, uses
"filepath" in a few more places where it previously didn't. also switches from
"filepath" to regular "path" package when handling mailbox names in a few
places, because those always use forward slashes, regardless of local file
system conventions. windows can handle forward slashes when opening files, so
test code that passes path strings with forward slashes straight to go stdlib
file i/o functions are left unchanged to reduce code churn. the regular
non-test code, or test code that uses path strings in places other than
standard i/o functions, does have the paths converted for consistent paths
(otherwise we would end up with paths with mixed forward/backward slashes in
log messages).
windows cannot dup a listening socket. for "mox localserve", it isn't
important, and we can work around the issue. the current approach for "mox
serve" (forking a process and passing file descriptors of listening sockets on
"privileged" ports) won't work on windows. perhaps it isn't needed on windows,
and any user can listen on "privileged" ports? that would be welcome.
on windows, os.Open cannot open a directory, so we cannot call Sync on it after
message delivery. a cursory internet search indicates that directories cannot
be synced on windows. the story is probably much more nuanced than that, with
long deep technical details/discussions/disagreement/confusion, like on unix.
for "mox localserve" we can get away with making syncdir a no-op.
the vendored dns resolver code is a copy of the go stdlib dns resolver, with
awareness of the "authentic data" (i.e. dnssec secure) added, as well as support
for enhanced dns errors, and looking up tlsa records (for dane). ideally it
would be upstreamed, but the chances seem slim.
dnssec-awareness is added to all packages, e.g. spf, dkim, dmarc, iprev. their
dnssec status is added to the Received message headers for incoming email.
but the main reason to add dnssec was for implementing dane. with dane, the
verification of tls certificates can be done through certificates/public keys
published in dns (in the tlsa records). this only makes sense (is trustworthy)
if those dns records can be verified to be authentic.
mox now applies dane to delivering messages over smtp. mox already implemented
mta-sts for webpki/pkix-verification of certificates against the (large) pool
of CA's, and still enforces those policies when present. but it now also checks
for dane records, and will verify those if present. if dane and mta-sts are
both absent, the regular opportunistic tls with starttls is still done. and the
fallback to plaintext is also still done.
mox also makes it easy to setup dane for incoming deliveries, so other servers
can deliver with dane tls certificate verification. the quickstart now
generates private keys that are used when requesting certificates with acme.
the private keys are pre-generated because they must be static and known during
setup, because their public keys must be published in tlsa records in dns.
autocert would generate private keys on its own, so had to be forked to add the
option to provide the private key when requesting a new certificate. hopefully
upstream will accept the change and we can drop the fork.
with this change, using the quickstart to setup a new mox instance, the checks
at internet.nl result in a 100% score, provided the domain is dnssec-signed and
the network doesn't have any issues.
we set the flag both for move in imap and in webmail.
this also ensures the "MailboxDestinedID", used for per-mailbox reputation
analysis, is set in more reject-situations. before this change, some rejects
(such as based on DMARC reject) wouldn't result in reputation being used after
having been moved the message out of the rejects mailbox.
in the future, we need more tests for scenario's like this...
for issue #63 reported by x8x
may also help with issue #64
increase() and rate() don't seem to assume a previous value of 0 when a vector
gets a first value for a label. you would think that an increase() on a
first-value mox_panic_total{"..."}=1 would return 1, and similar for rate(), but
that doesn't appear to be the behaviour. so we just explicitly initialize the
count to 0 for each possible label value. mox has more vector metrics, but
panics feels like the most important, and it's too much code to initialize them
all, for all combinations of label values. there is probably a better way that
fixes this for all cases...
we match messages to their parents based on the "references" and "in-reply-to"
headers (requiring the same base subject), and in absense of those headers we
also by only base subject (against messages received max 4 weeks ago).
we store a threadid with messages. all messages in a thread have the same
threadid. messages also have a "thread parent ids", which holds all id's of
parent messages up to the thread root. then there is "thread missing link",
which is set when a referenced immediate parent wasn't found (but possibly
earlier ancestors can still be found and will be in thread parent ids".
threads can be muted: newly delivered messages are automatically marked as
read/seen. threads can be marked as collapsed: if set, the webmail collapses
the thread to a single item in the basic threading view (default is to expand
threads). the muted and collapsed fields are copied from their parent on
message delivery.
the threading is implemented in the webmail. the non-threading mode still works
as before. the new default threading mode "unread" automatically expands only
the threads with at least one unread (not seen) meessage. the basic threading
mode "on" expands all threads except when explicitly collapsed (as saved in the
thread collapsed field). new shortcuts for navigation/interaction threads have
been added, e.g. go to previous/next thread root, toggle collapse/expand of
thread (or double click), toggle mute of thread. some previous shortcuts have
changed, see the help for details.
the message threading are added with an explicit account upgrade step,
automatically started when an account is opened. the upgrade is done in the
background because it will take too long for large mailboxes to block account
operations. the upgrade takes two steps: 1. updating all message records in the
database to add a normalized message-id and thread base subject (with "re:",
"fwd:" and several other schemes stripped). 2. going through all messages in
the database again, reading the "references" and "in-reply-to" headers from
disk, and matching against their parents. this second step is also done at the
end of each import of mbox/maildir mailboxes. new deliveries are matched
immediately against other existing messages, currently no attempt is made to
rematch previously delivered messages (which could be useful for related
messages being delivered out of order).
the threading is not yet exposed over imap.
for submission, we don't care about the value. users typically won't be able to
easily fix the errors (of their mail client software). so we just ignore the
domain/ip address, unless in pedantic mode.
this also parses "additional information after literal addresses" more
strictly/correctly.
for issue #55 by gimpf, thanks for the report!
the recent webmail addition added localserve local delivery in queue.Add, so we
just that for smtpserver too.
and don't drop incoming smtp deliver messages, but deliver as normal.
without public ip's, the generated mox config will try to listen on 0.0.0.0 and
::, but because there is already a listener for 127.0.0.1:80 (and possibly
others), a bind for 0.0.0.0:80 will fail. explicit public ip's are needed.
the public http listener is useful for ACME validation over http.
for issue #52
this is based on @bobobo1618's PR #50. bobobo1618 had the right idea, i tried
including an "is forwarded email" configuration option but that indeed became
too tightly coupled. the "is forwarded" option is still planned, but it is
separate from the "accept rejects to mailbox" config option, because one could
still want to push back on forwarded spam messages.
we do an actual accept, delivering to a configured mailbox, instead of storing
to the rejects mailbox where messages can automatically be removed from. one
of the goals of mox is not pretend to accept email while actually junking it.
users can still configure delivery to a junk folder (as was already possible),
but aren't deleted automatically. there is still an X-Mox-Reason header in the
message, and a log line about accepting the reject, but otherwise it is
registered and treated as an (smtp) accept.
the ruleset mailbox is still required to keep that explicit. users can specify
Inbox again.
hope this is good enough for PR #50, otherwise we'll change it.
soon, we can have multiple rejects mailboxes. and checking against the
configured rejects mailbox name wasn't foolproof to begin with, because it may
have changed between delivery to the rejects mailbox and the message being
moved.
after upgrading, messages currently in rejects mailboxes don't have IsReject
set, so they don't get the special rejecs treatment when being moved. they are
removed from the rejects mailbox after some time though, and newly added
rejects will be treated correctly. so this means some existing messages wrongly
delivered to the rejects mailbox, and moved out, aren't used (for a positive
signal) for future deliveries. saves a bit of complexity in the
implementation. i think the tradeoff is worth it.
related to discussion in issue #50
the bulk of a message is stored on disk. a message prefix is stored in the
database (for prefixed headers like "Received:"). this adds a check to ensure
Size = prefix length + on-disk file size.
verifydata also checks for this now.
and one older and one new (since yesterday) bug was found. the first when
appending a message without a header/body section (uncommon). the second when
sending messages from webmail with localserve (uncommon).
it was far down on the roadmap, but implemented earlier, because it's
interesting, and to help prepare for a jmap implementation. for jmap we need to
implement more client-like functionality than with just imap. internal data
structures need to change. jmap has lots of other requirements, so it's already
a big project. by implementing a webmail now, some of the required data
structure changes become clear and can be made now, so the later jmap
implementation can do things similarly to the webmail code. the webmail
frontend and webmail are written together, making their interface/api much
smaller and simpler than jmap.
one of the internal changes is that we now keep track of per-mailbox
total/unread/unseen/deleted message counts and mailbox sizes. keeping this
data consistent after any change to the stored messages (through the code base)
is tricky, so mox now has a consistency check that verifies the counts are
correct, which runs only during tests, each time an internal account reference
is closed. we have a few more internal "changes" that are propagated for the
webmail frontend (that imap doesn't have a way to propagate on a connection),
like changes to the special-use flags on mailboxes, and used keywords in a
mailbox. more changes that will be required have revealed themselves while
implementing the webmail, and will be implemented next.
the webmail user interface is modeled after the mail clients i use or have
used: thunderbird, macos mail, mutt; and webmails i normally only use for
testing: gmail, proton, yahoo, outlook. a somewhat technical user is assumed,
but still the goal is to make this webmail client easy to use for everyone. the
user interface looks like most other mail clients: a list of mailboxes, a
search bar, a message list view, and message details. there is a top/bottom and
a left/right layout for the list/message view, default is automatic based on
screen size. the panes can be resized by the user. buttons for actions are just
text, not icons. clicking a button briefly shows the shortcut for the action in
the bottom right, helping with learning to operate quickly. any text that is
underdotted has a title attribute that causes more information to be displayed,
e.g. what a button does or a field is about. to highlight potential phishing
attempts, any text (anywhere in the webclient) that switches unicode "blocks"
(a rough approximation to (language) scripts) within a word is underlined
orange. multiple messages can be selected with familiar ui interaction:
clicking while holding control and/or shift keys. keyboard navigation works
with arrows/page up/down and home/end keys, and also with a few basic vi-like
keys for list/message navigation. we prefer showing the text instead of
html (with inlined images only) version of a message. html messages are shown
in an iframe served from an endpoint with CSP headers to prevent dangerous
resources (scripts, external images) from being loaded. the html is also
sanitized, with javascript removed. a user can choose to load external
resources (e.g. images for tracking purposes).
the frontend is just (strict) typescript, no external frameworks. all
incoming/outgoing data is typechecked, both the api request parameters and
response types, and the data coming in over SSE. the types and checking code
are generated with sherpats, which uses the api definitions generated by
sherpadoc based on the Go code. so types from the backend are automatically
propagated to the frontend. since there is no framework to automatically
propagate properties and rerender components, changes coming in over the SSE
connection are propagated explicitly with regular function calls. the ui is
separated into "views", each with a "root" dom element that is added to the
visible document. these views have additional functions for getting changes
propagated, often resulting in the view updating its (internal) ui state (dom).
we keep the frontend compilation simple, it's just a few typescript files that
get compiled (combined and types stripped) into a single js file, no additional
runtime code needed or complicated build processes used. the webmail is served
is served from a compressed, cachable html file that includes style and the
javascript, currently just over 225kb uncompressed, under 60kb compressed (not
minified, including comments). we include the generated js files in the
repository, to keep Go's easily buildable self-contained binaries.
authentication is basic http, as with the account and admin pages. most data
comes in over one long-term SSE connection to the backend. api requests signal
which mailbox/search/messages are requested over the SSE connection. fetching
individual messages, and making changes, are done through api calls. the
operations are similar to imap, so some code has been moved from package
imapserver to package store. the future jmap implementation will benefit from
these changes too. more functionality will probably be moved to the store
package in the future.
the quickstart enables webmail on the internal listener by default (for new
installs). users can enable it on the public listener if they want to. mox
localserve enables it too. to enable webmail on existing installs, add settings
like the following to the listeners in mox.conf, similar to AccountHTTP(S):
WebmailHTTP:
Enabled: true
WebmailHTTPS:
Enabled: true
special thanks to liesbeth, gerben, andrii for early user feedback.
there is plenty still to do, see the list at the top of webmail/webmail.ts.
feedback welcome as always.
the space is explicitly mentioned as not valid in rfc 5321, but it clients do
send it, such as microsoft outlook 365 apps for enterprise. no need to punish
such users, we'll allow it. but only for submission, not regular smtp, because
it is normally a sign of a spammer. we still don't allow it in pedantic mode
(as used by localserve).
for issue #51 by hmfaysal, thanks for reporting and testing!
for conditional storing and quick resynchronisation (not sure if mail clients are actually using it that).
each message now has a "modseq". it is increased for each change. with
condstore, imap clients can request changes since a certain modseq. that
already allows quickly finding changes since a previous connection. condstore
also allows storing (e.g. setting new message flags) only when the modseq of a
message hasn't changed.
qresync should make it fast for clients to get a full list of changed messages
for a mailbox, including removals.
we now also keep basic metadata of messages that have been removed (expunged).
just enough (uid, modseq) to tell client that the messages have been removed.
this does mean we have to be careful when querying messages from the database.
we must now often filter the expunged messages out.
we also keep "createseq", the modseq when a message was created. this will be
useful for the jmap implementation.
the warnings that remained were either unused code that i wanted to use in the
future, or other type's of todo's. i've been mentally ignoring them, assuming i
would get back to them soon enough to fix them. but that hasn't happened yet,
and it's better to have a clean list with only actual isses.
so mail user agents will show DSNs threaded/grouped with the original message.
we store the MessageID in the message queue, so we have the value within reach
when we need it.
i saw a references header in a DSN from gmail on a test account. makes sense to me.
an EHLO ipv4 address looks like this: "[1.2.3.4]". for ipv6, the syntax is:
"[IPv6🔡:1]". mail user agents aren't as careful in compliance as smtp
servers. for incoming messages from smtp servers, we want to be strict (we're
eager to find a reason not to accept spam messages, and not adhering to the
standards is usually a strong spam signal), but there is no reason to punish
authenticated users.
for the syntax requirements, see ABNF rule "address-literal" in rfc 5321.
for issue #48 by @bobobo1618, thanks!
we could make more types of delays configurable. the current approach isn't
great, as it results in an a default value of "0s" in the config file, while
the actual default is 15s (which is documented just above, but still).
the default transport is still just "direct delivery", where we connect to the
destination domain's MX servers.
other transports are:
- regular smtp without authentication, this is relaying to a smarthost.
- submission with authentication, e.g. to a third party email sending service.
- direct delivery, but with with connections going through a socks proxy. this
can be helpful if your ip is blocked, you need to get email out, and you have
another IP that isn't blocked.
keep in mind that for all of the above, appropriate SPF/DKIM settings have to
be configured. the "dnscheck" for a domain does a check for any SOCKS IP in the
SPF record. SPF for smtp/submission (ranges? includes?) and any DKIM
requirements cannot really be checked.
which transport is used can be configured through routes. routes can be set on
an account, a domain, or globally. the routes are evaluated in that order, with
the first match selecting the transport. these routes are evaluated for each
delivery attempt. common selection criteria are recipient domain and sender
domain, but also which delivery attempt this is. you could configured mox to
attempt sending through a 3rd party from the 4th attempt onwards.
routes and transports are optional. if no route matches, or an empty/zero
transport is selected, normal direct delivery is done.
we could already "submit" emails with 3rd party accounts with "sendmail". but
we now support more SASL authentication mechanisms with SMTP (not only PLAIN,
but also SCRAM-SHA-256, SCRAM-SHA-1 and CRAM-MD5), which sendmail now also
supports. sendmail will use the most secure mechanism supported by the server,
or the explicitly configured mechanism.
for issue #36 by dmikushin. also based on earlier discussion on hackernews.
we were adding the missing date and/or message-id header, but didn't sign it.
and the default dkim signing config is to (over)sign those headers. so that was
causing errors with bad signatures.
found while setting up automated tests for quickstart, while sending a very
basic message between a fresh install.
so external tools (like fail2ban) can monitor the logs and block ip's of bots.
for issue #30 by inigoserna, though i'm not sure i interpreted the suggestion correctly.
the backup command will make consistent snapshots of all the database files. i
had been copying the db files before, and it usually works. but if the file is
modified during the backup, it is inconsistent and is likely to generate errors
when reading (can be at any moment in the future, when reading some db page).
"mox backup" opens the database file and writes out a copy in a transaction.
it also duplicates the message files.
before doing a restore, you could run "mox verifydata" on the to-be-restored
"data" directory. it check the database files, and compares the message files
with the database.
the new "gentestdata" subcommand generates a basic "data" directory, with a
queue and a few accounts. we will use it in the future along with "verifydata"
to test upgrades from old version to the latest version. both when going to the
next version, and when skipping several versions. the script test-upgrades.sh
executes these tests and doesn't do anything at the moment, because no releases
have this subcommand yet.
inspired by a failed upgrade attempt of a pre-release version.
dmarc verifiers will only accept a dkim signature if the domain the message From
header matches the domain of the signature (i.e. it is "aligned").
i hadn't run into this before and when testing because thunderbird sets the
"smtp mail from" to the same address as a custom "message from" header. but
other mail clients don't have to do that.
should fix issue #22
by specifying a "destination" in an account that is just "@" followed by the
domain, e.g. "@example.org". messages are only delivered to the catchall
address when no regular destination matches (taking the per-domain
catchall-separator and case-sensisitivity into account).
for issue #18
by default 1000 messages per day, and to max 200 first-time receivers.
i don't think a person would reach those limits. a compromised account abused
by spammers could easily reach that limit. this prevents further damage.
the error message you will get is quite clear, pointing to the configuration
parameter that should be changed.
it must be completely parsable.
normally, if we receive a message that we cannot fully parse, we accept it and
treat it as opaque application/octet-stream.
also make it more clear that localserve accepts email intended for any email
address.
localserve creates a config for listening on localhost for
imap/smtp/submission/http, on port numbers 1000 + the common service port
numbers. all incoming email is accepted (if checks pass), and a few pattern in
localparts are recognized and result in delivery errors.
this is quite common on the internet. the other side may be trying some other
protocol, e.g. http, or some common vulnerability. we don't want to spam our
own logs with multiple invalid lines. if the first command is valid, but later
are not, we'll keep trying to process them. so this only affects protocol
sessions that are very likely not smtp/imap.
also remove a few more sleeps during tests, making imapserver and smtpserver tests a bit faster.
the idea of the rejects mailbox is to show messages that were rejected. you can
look there, and if you see a message that should have been delivered, you can
move it to your inbox or archive. next time a deliver attempt by that user is
attempted, they should be accepted, because you corrected the reject. but that
wasn't happening, because the reputation-calculation is per-delivery mailbox
(e.g. Inbox) and we look at MailboxOrigID when calculating the reputation. and
that was set to the Rejects mailbox id, so the message wasn't considered. the
same applies to moving messages from Rejects to Junk (to train your filter).
we now keep track of a MailboxDestinedID, that is set to the mailbox that we
would have delivered to if we would not have rejected the message. then, when a
message is moved out of the Rejects mailbox, we change MailboxOrigID to
MailboxDestinedID. this essentially makes the message look like it was
delivered normally.
makes it easier to run on bsd's, where you cannot (easily?) let non-root users
bind to ports <1024. starting as root also paves the way for future improvements
with privilege separation.
unfortunately, this requires changes to how you start mox. though mox will help
by automatically fix up dir/file permissions/ownership.
if you start mox from the systemd unit file, you should update it so it starts
as root and adds a few additional capabilities:
# first update the mox binary, then, as root:
./mox config printservice >mox.service
systemctl daemon-reload
systemctl restart mox
journalctl -f -u mox &
# you should see mox start up, with messages about fixing permissions on dirs/files.
if you used the recommended config/ and data/ directory, in a directory just for
mox, and with the mox user called "mox", this should be enough.
if you don't want mox to modify dir/file permissions, set "NoFixPermissions:
true" in mox.conf.
if you named the mox user something else than mox, e.g. "_mox", add "User: _mox"
to mox.conf.
if you created a shared service user as originally suggested, you may want to
get rid of that as it is no longer useful and may get in the way. e.g. if you
had /home/service/mox with a "service" user, that service user can no longer
access any files: only mox and root can.
this also adds scripts for building mox docker images for alpine-supported
platforms.
the "restart" subcommand has been removed. it wasn't all that useful and got in
the way.
and another change: when adding a domain while mtasts isn't enabled, don't add
the per-domain mtasts config, as it would cause failure to add the domain.
based on report from setting up mox on openbsd from mteege.
and based on issue #3. thanks for the feedback!
so users can easily take their email out of somewhere else, and import it into mox.
this goes a little way to give feedback as the import progresses: upload
progress is shown (surprisingly, browsers aren't doing this...), imported
mailboxes/messages are counted (batched) and import issues/warnings are
displayed, all sent over an SSE connection. an import token is stored in
sessionstorage. if you reload the page (e.g. after a connection error), the
browser will reconnect to the running import and show its progress again. and
you can just abort the import before it is finished and committed, and nothing
will have changed.
this also imports flags/keywords from mbox files.
ideally both account & admin web pages should be on non-public ips (e.g. a
wireguard tunnel). but during setup, users may not have that set up, and they
may want to configure the admin/account pages on their public ip's. the auth
rate limiting should make it less of issue.
users can now also only put the account web page publicly available. useful for
if you're the admin and you have a vpn connection, but your other/external
users do not have a vpn into your mail server. to make the account page more
easily findable, the http root serves the account page. the admin page is still
at /admin/, to prevent clash with potential account pages, but if no account
page is present, you are helpfully redirected from / to /admin/.
this also adds a prometheus metric counting how often auth attempts have been
rate limited.
the previous default, marking the messages as junk had the interesting effect
of training the junk filter. rejecting could have been the result of the
sending IP being in the DNSBL. so the DNSBL helped to automatically train the
junk filter. perhaps we can keep that in the future and just not take messages
from the rejects mailbox into account when evaluating the reputation for
incoming deliveries.
before, we used heuristics to decide when to train/untrain a message as junk or
nonjunk: the message had to be seen, be in certain mailboxes. then if a message
was marked as junk, it was junk. and otherwise it was nonjunk. this wasn't good
enough: you may want to keep some messages around as neither junk or nonjunk.
and that wasn't possible.
ideally, we would just look at the imap $Junk and $NotJunk flags. the problem
is that mail clients don't set these flags, or don't make it easy. thunderbird
can set the flags based on its own bayesian filter. it has a shortcut for
marking Junk and moving it to the junk folder (good), but the counterpart of
notjunk only marks a message as notjunk without showing in the UI that it was
marked as notjunk. there is also no "move and mark as notjunk" mechanism. e.g.
"archive" does not mark a message as notjunk. ios mail and mutt don't appear to
have any way to see or change the $Junk and $NotJunk flags.
what email clients do have is the ability to move messages to other
mailboxes/folders. so mox now has a mechanism that allows you to configure
mailboxes that automatically set $Junk or $NotJunk (or clear both) when a
message is moved/copied/delivered to that folder. e.g. a mailbox called junk or
spam or rejects marks its messags as junk. inbox, postmaster, dmarc, tlsrpt,
neutral* mark their messages as neither junk or notjunk. other folders mark
their messages as notjunk. e.g. list/*, archive. this functionality is
optional, but enabled with the quickstart and for new accounts.
also, mox now keeps track of the previous training of a message and will only
untrain/train if needed. before, there probably have been duplicate or missing
(un)trainings.
this also includes a new subcommand "retrain" to recreate the junkfilter for an
account. you should run it after updating to this version. and you should
probably also modify your account config to include the AutomaticJunkFlags.
similar to greylisting, but not quite the same: with greylisting you would
always reject the first delivery attempt with a temporary failure. with the
hope that spammers won't retry their deliveries. the spams i've been receiving
seem to be quite consistent though. and we would keep rejecting them anyway.
we slow down the spammy connections to waste some of the resources of a
spammer. this may slow their campaigns down a bit, leaving a bit more time to
take measures.
we do the same with connections that have their 3rd authentication failure,
typically password guess attempts.
when we accept a message by a first-time sender, we sleep for 15 seconds before
actually delivering them. known-good senders don't have to wait. if the message
turns out to be a spammer, at least we've consumed one of their connections,
and they cannot deliver at too high a rate to us because of the max open
connection limit.
limiting is done based on remote ip's, with 3 ip mask variants to limit networks
of machines. often with two windows, enabling short bursts of activity, but not
sustained high activity. currently only for imap and smtp, not yet http.
limits are currently based on:
- number of open connections
- connection rate
- limits after authentication failures. too many failures, and new connections will be dropped.
- rate of delivery in total number of messages
- rate of delivery in total size of messages
the limits on connections and authentication failures are in-memory. the limits
on delivery of messages are based on stored messages.
the limits themselves are not yet configurable, let's use this first.
in the future, we may also want to have stricter limits for senders without any
reputation.
and change thunderbird autoconfiguration to use it.
unfortunately, for microsoft autodiscover, there appears to be no way to
request secure password negotiation. so it will default to plain text auth.
cram-md5 is less secure than scram-sha-*, but thunderbird does not yet support
scram auth. it currently chooses "plain", sending the literal password over the
connection (which is TLS-protected, but we don't want to receive clear text
passwords). in short, cram-md5 is better than nothing...
for cram-md5 to work, a new set of derived credentials need to be stored in the
database. so you need to save your password again to make it work. this was
also the case with the scram-sha-1 addition, but i forgot to mention it then.
the idea is that clients may not support SCRAM-SHA-256, but may support
SCRAM-SHA-1. if they do support the 256 variant, they'll use it.
unfortunately, thunderbird does not support scram-sha-1 either.
named "traceauth" and "tracedata".
with this, you can (almost) enable trace logging without fear of logging
sensitive data or ddos'ing your log server.
the caveat is that the imap login command has already printed the line as
regular trace before we can decide it should not be. can be fixed soon.
