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.
