diff --git a/webmail/api.json b/webmail/api.json
index fc69e76..0ed9646 100644
--- a/webmail/api.json
+++ b/webmail/api.json
@@ -1358,6 +1358,13 @@
 					"Typewords": [
 						"string"
 					]
+				},
+				{
+					"Name": "Version",
+					"Docs": "",
+					"Typewords": [
+						"string"
+					]
 				}
 			]
 		},
diff --git a/webmail/api.ts b/webmail/api.ts
index ba24727..f0f7980 100644
--- a/webmail/api.ts
+++ b/webmail/api.ts
@@ -199,6 +199,7 @@ export interface EventStart {
 	MailboxName: string
 	Mailboxes?: Mailbox[] | null
 	RejectsMailbox: string
+	Version: string
 }
 
 // DomainAddressConfig has the address (localpart) configuration for a domain, so
@@ -532,7 +533,7 @@ export const types: TypenameMap = {
 	"ForwardAttachments": {"Name":"ForwardAttachments","Docs":"","Fields":[{"Name":"MessageID","Docs":"","Typewords":["int64"]},{"Name":"Paths","Docs":"","Typewords":["[]","[]","int32"]}]},
 	"Mailbox": {"Name":"Mailbox","Docs":"","Fields":[{"Name":"ID","Docs":"","Typewords":["int64"]},{"Name":"Name","Docs":"","Typewords":["string"]},{"Name":"UIDValidity","Docs":"","Typewords":["uint32"]},{"Name":"UIDNext","Docs":"","Typewords":["UID"]},{"Name":"Archive","Docs":"","Typewords":["bool"]},{"Name":"Draft","Docs":"","Typewords":["bool"]},{"Name":"Junk","Docs":"","Typewords":["bool"]},{"Name":"Sent","Docs":"","Typewords":["bool"]},{"Name":"Trash","Docs":"","Typewords":["bool"]},{"Name":"Keywords","Docs":"","Typewords":["[]","string"]},{"Name":"HaveCounts","Docs":"","Typewords":["bool"]},{"Name":"Total","Docs":"","Typewords":["int64"]},{"Name":"Deleted","Docs":"","Typewords":["int64"]},{"Name":"Unread","Docs":"","Typewords":["int64"]},{"Name":"Unseen","Docs":"","Typewords":["int64"]},{"Name":"Size","Docs":"","Typewords":["int64"]}]},
 	"RecipientSecurity": {"Name":"RecipientSecurity","Docs":"","Fields":[{"Name":"STARTTLS","Docs":"","Typewords":["SecurityResult"]},{"Name":"MTASTS","Docs":"","Typewords":["SecurityResult"]},{"Name":"DNSSEC","Docs":"","Typewords":["SecurityResult"]},{"Name":"DANE","Docs":"","Typewords":["SecurityResult"]},{"Name":"RequireTLS","Docs":"","Typewords":["SecurityResult"]}]},
-	"EventStart": {"Name":"EventStart","Docs":"","Fields":[{"Name":"SSEID","Docs":"","Typewords":["int64"]},{"Name":"LoginAddress","Docs":"","Typewords":["MessageAddress"]},{"Name":"Addresses","Docs":"","Typewords":["[]","MessageAddress"]},{"Name":"DomainAddressConfigs","Docs":"","Typewords":["{}","DomainAddressConfig"]},{"Name":"MailboxName","Docs":"","Typewords":["string"]},{"Name":"Mailboxes","Docs":"","Typewords":["[]","Mailbox"]},{"Name":"RejectsMailbox","Docs":"","Typewords":["string"]}]},
+	"EventStart": {"Name":"EventStart","Docs":"","Fields":[{"Name":"SSEID","Docs":"","Typewords":["int64"]},{"Name":"LoginAddress","Docs":"","Typewords":["MessageAddress"]},{"Name":"Addresses","Docs":"","Typewords":["[]","MessageAddress"]},{"Name":"DomainAddressConfigs","Docs":"","Typewords":["{}","DomainAddressConfig"]},{"Name":"MailboxName","Docs":"","Typewords":["string"]},{"Name":"Mailboxes","Docs":"","Typewords":["[]","Mailbox"]},{"Name":"RejectsMailbox","Docs":"","Typewords":["string"]},{"Name":"Version","Docs":"","Typewords":["string"]}]},
 	"DomainAddressConfig": {"Name":"DomainAddressConfig","Docs":"","Fields":[{"Name":"LocalpartCatchallSeparator","Docs":"","Typewords":["string"]},{"Name":"LocalpartCaseSensitive","Docs":"","Typewords":["bool"]}]},
 	"EventViewErr": {"Name":"EventViewErr","Docs":"","Fields":[{"Name":"ViewID","Docs":"","Typewords":["int64"]},{"Name":"RequestID","Docs":"","Typewords":["int64"]},{"Name":"Err","Docs":"","Typewords":["string"]}]},
 	"EventViewReset": {"Name":"EventViewReset","Docs":"","Fields":[{"Name":"ViewID","Docs":"","Typewords":["int64"]},{"Name":"RequestID","Docs":"","Typewords":["int64"]}]},
diff --git a/webmail/msg.js b/webmail/msg.js
index e4840c9..2b292f2 100644
--- a/webmail/msg.js
+++ b/webmail/msg.js
@@ -67,7 +67,7 @@ var api;
 		"ForwardAttachments": { "Name": "ForwardAttachments", "Docs": "", "Fields": [{ "Name": "MessageID", "Docs": "", "Typewords": ["int64"] }, { "Name": "Paths", "Docs": "", "Typewords": ["[]", "[]", "int32"] }] },
 		"Mailbox": { "Name": "Mailbox", "Docs": "", "Fields": [{ "Name": "ID", "Docs": "", "Typewords": ["int64"] }, { "Name": "Name", "Docs": "", "Typewords": ["string"] }, { "Name": "UIDValidity", "Docs": "", "Typewords": ["uint32"] }, { "Name": "UIDNext", "Docs": "", "Typewords": ["UID"] }, { "Name": "Archive", "Docs": "", "Typewords": ["bool"] }, { "Name": "Draft", "Docs": "", "Typewords": ["bool"] }, { "Name": "Junk", "Docs": "", "Typewords": ["bool"] }, { "Name": "Sent", "Docs": "", "Typewords": ["bool"] }, { "Name": "Trash", "Docs": "", "Typewords": ["bool"] }, { "Name": "Keywords", "Docs": "", "Typewords": ["[]", "string"] }, { "Name": "HaveCounts", "Docs": "", "Typewords": ["bool"] }, { "Name": "Total", "Docs": "", "Typewords": ["int64"] }, { "Name": "Deleted", "Docs": "", "Typewords": ["int64"] }, { "Name": "Unread", "Docs": "", "Typewords": ["int64"] }, { "Name": "Unseen", "Docs": "", "Typewords": ["int64"] }, { "Name": "Size", "Docs": "", "Typewords": ["int64"] }] },
 		"RecipientSecurity": { "Name": "RecipientSecurity", "Docs": "", "Fields": [{ "Name": "STARTTLS", "Docs": "", "Typewords": ["SecurityResult"] }, { "Name": "MTASTS", "Docs": "", "Typewords": ["SecurityResult"] }, { "Name": "DNSSEC", "Docs": "", "Typewords": ["SecurityResult"] }, { "Name": "DANE", "Docs": "", "Typewords": ["SecurityResult"] }, { "Name": "RequireTLS", "Docs": "", "Typewords": ["SecurityResult"] }] },
-		"EventStart": { "Name": "EventStart", "Docs": "", "Fields": [{ "Name": "SSEID", "Docs": "", "Typewords": ["int64"] }, { "Name": "LoginAddress", "Docs": "", "Typewords": ["MessageAddress"] }, { "Name": "Addresses", "Docs": "", "Typewords": ["[]", "MessageAddress"] }, { "Name": "DomainAddressConfigs", "Docs": "", "Typewords": ["{}", "DomainAddressConfig"] }, { "Name": "MailboxName", "Docs": "", "Typewords": ["string"] }, { "Name": "Mailboxes", "Docs": "", "Typewords": ["[]", "Mailbox"] }, { "Name": "RejectsMailbox", "Docs": "", "Typewords": ["string"] }] },
+		"EventStart": { "Name": "EventStart", "Docs": "", "Fields": [{ "Name": "SSEID", "Docs": "", "Typewords": ["int64"] }, { "Name": "LoginAddress", "Docs": "", "Typewords": ["MessageAddress"] }, { "Name": "Addresses", "Docs": "", "Typewords": ["[]", "MessageAddress"] }, { "Name": "DomainAddressConfigs", "Docs": "", "Typewords": ["{}", "DomainAddressConfig"] }, { "Name": "MailboxName", "Docs": "", "Typewords": ["string"] }, { "Name": "Mailboxes", "Docs": "", "Typewords": ["[]", "Mailbox"] }, { "Name": "RejectsMailbox", "Docs": "", "Typewords": ["string"] }, { "Name": "Version", "Docs": "", "Typewords": ["string"] }] },
 		"DomainAddressConfig": { "Name": "DomainAddressConfig", "Docs": "", "Fields": [{ "Name": "LocalpartCatchallSeparator", "Docs": "", "Typewords": ["string"] }, { "Name": "LocalpartCaseSensitive", "Docs": "", "Typewords": ["bool"] }] },
 		"EventViewErr": { "Name": "EventViewErr", "Docs": "", "Fields": [{ "Name": "ViewID", "Docs": "", "Typewords": ["int64"] }, { "Name": "RequestID", "Docs": "", "Typewords": ["int64"] }, { "Name": "Err", "Docs": "", "Typewords": ["string"] }] },
 		"EventViewReset": { "Name": "EventViewReset", "Docs": "", "Fields": [{ "Name": "ViewID", "Docs": "", "Typewords": ["int64"] }, { "Name": "RequestID", "Docs": "", "Typewords": ["int64"] }] },
diff --git a/webmail/text.js b/webmail/text.js
index 2757411..e2d02f8 100644
--- a/webmail/text.js
+++ b/webmail/text.js
@@ -67,7 +67,7 @@ var api;
 		"ForwardAttachments": { "Name": "ForwardAttachments", "Docs": "", "Fields": [{ "Name": "MessageID", "Docs": "", "Typewords": ["int64"] }, { "Name": "Paths", "Docs": "", "Typewords": ["[]", "[]", "int32"] }] },
 		"Mailbox": { "Name": "Mailbox", "Docs": "", "Fields": [{ "Name": "ID", "Docs": "", "Typewords": ["int64"] }, { "Name": "Name", "Docs": "", "Typewords": ["string"] }, { "Name": "UIDValidity", "Docs": "", "Typewords": ["uint32"] }, { "Name": "UIDNext", "Docs": "", "Typewords": ["UID"] }, { "Name": "Archive", "Docs": "", "Typewords": ["bool"] }, { "Name": "Draft", "Docs": "", "Typewords": ["bool"] }, { "Name": "Junk", "Docs": "", "Typewords": ["bool"] }, { "Name": "Sent", "Docs": "", "Typewords": ["bool"] }, { "Name": "Trash", "Docs": "", "Typewords": ["bool"] }, { "Name": "Keywords", "Docs": "", "Typewords": ["[]", "string"] }, { "Name": "HaveCounts", "Docs": "", "Typewords": ["bool"] }, { "Name": "Total", "Docs": "", "Typewords": ["int64"] }, { "Name": "Deleted", "Docs": "", "Typewords": ["int64"] }, { "Name": "Unread", "Docs": "", "Typewords": ["int64"] }, { "Name": "Unseen", "Docs": "", "Typewords": ["int64"] }, { "Name": "Size", "Docs": "", "Typewords": ["int64"] }] },
 		"RecipientSecurity": { "Name": "RecipientSecurity", "Docs": "", "Fields": [{ "Name": "STARTTLS", "Docs": "", "Typewords": ["SecurityResult"] }, { "Name": "MTASTS", "Docs": "", "Typewords": ["SecurityResult"] }, { "Name": "DNSSEC", "Docs": "", "Typewords": ["SecurityResult"] }, { "Name": "DANE", "Docs": "", "Typewords": ["SecurityResult"] }, { "Name": "RequireTLS", "Docs": "", "Typewords": ["SecurityResult"] }] },
-		"EventStart": { "Name": "EventStart", "Docs": "", "Fields": [{ "Name": "SSEID", "Docs": "", "Typewords": ["int64"] }, { "Name": "LoginAddress", "Docs": "", "Typewords": ["MessageAddress"] }, { "Name": "Addresses", "Docs": "", "Typewords": ["[]", "MessageAddress"] }, { "Name": "DomainAddressConfigs", "Docs": "", "Typewords": ["{}", "DomainAddressConfig"] }, { "Name": "MailboxName", "Docs": "", "Typewords": ["string"] }, { "Name": "Mailboxes", "Docs": "", "Typewords": ["[]", "Mailbox"] }, { "Name": "RejectsMailbox", "Docs": "", "Typewords": ["string"] }] },
+		"EventStart": { "Name": "EventStart", "Docs": "", "Fields": [{ "Name": "SSEID", "Docs": "", "Typewords": ["int64"] }, { "Name": "LoginAddress", "Docs": "", "Typewords": ["MessageAddress"] }, { "Name": "Addresses", "Docs": "", "Typewords": ["[]", "MessageAddress"] }, { "Name": "DomainAddressConfigs", "Docs": "", "Typewords": ["{}", "DomainAddressConfig"] }, { "Name": "MailboxName", "Docs": "", "Typewords": ["string"] }, { "Name": "Mailboxes", "Docs": "", "Typewords": ["[]", "Mailbox"] }, { "Name": "RejectsMailbox", "Docs": "", "Typewords": ["string"] }, { "Name": "Version", "Docs": "", "Typewords": ["string"] }] },
 		"DomainAddressConfig": { "Name": "DomainAddressConfig", "Docs": "", "Fields": [{ "Name": "LocalpartCatchallSeparator", "Docs": "", "Typewords": ["string"] }, { "Name": "LocalpartCaseSensitive", "Docs": "", "Typewords": ["bool"] }] },
 		"EventViewErr": { "Name": "EventViewErr", "Docs": "", "Fields": [{ "Name": "ViewID", "Docs": "", "Typewords": ["int64"] }, { "Name": "RequestID", "Docs": "", "Typewords": ["int64"] }, { "Name": "Err", "Docs": "", "Typewords": ["string"] }] },
 		"EventViewReset": { "Name": "EventViewReset", "Docs": "", "Fields": [{ "Name": "ViewID", "Docs": "", "Typewords": ["int64"] }, { "Name": "RequestID", "Docs": "", "Typewords": ["int64"] }] },
diff --git a/webmail/view.go b/webmail/view.go
index 3b02486..e2770cb 100644
--- a/webmail/view.go
+++ b/webmail/view.go
@@ -30,6 +30,7 @@ import (
 	"github.com/mjl-/mox/mlog"
 	"github.com/mjl-/mox/mox-"
 	"github.com/mjl-/mox/moxio"
+	"github.com/mjl-/mox/moxvar"
 	"github.com/mjl-/mox/smtp"
 	"github.com/mjl-/mox/store"
 )
@@ -214,6 +215,7 @@ type EventStart struct {
 	MailboxName          string
 	Mailboxes            []store.Mailbox
 	RejectsMailbox       string
+	Version              string
 }
 
 // DomainAddressConfig has the address (localpart) configuration for a domain, so
@@ -721,7 +723,7 @@ func serveEvents(ctx context.Context, log *mlog.Log, w http.ResponseWriter, r *h
 	}
 
 	// Write first event, allowing client to fill its UI with mailboxes.
-	start := EventStart{sse.ID, loginAddress, addresses, domainAddressConfigs, mailbox.Name, mbl, accConf.RejectsMailbox}
+	start := EventStart{sse.ID, loginAddress, addresses, domainAddressConfigs, mailbox.Name, mbl, accConf.RejectsMailbox, moxvar.Version}
 	writer.xsendEvent(ctx, log, "start", start)
 
 	// The goroutine doing the querying will send messages on these channels, which
diff --git a/webmail/webmail.js b/webmail/webmail.js
index cfa8c48..a78a3a0 100644
--- a/webmail/webmail.js
+++ b/webmail/webmail.js
@@ -67,7 +67,7 @@ var api;
 		"ForwardAttachments": { "Name": "ForwardAttachments", "Docs": "", "Fields": [{ "Name": "MessageID", "Docs": "", "Typewords": ["int64"] }, { "Name": "Paths", "Docs": "", "Typewords": ["[]", "[]", "int32"] }] },
 		"Mailbox": { "Name": "Mailbox", "Docs": "", "Fields": [{ "Name": "ID", "Docs": "", "Typewords": ["int64"] }, { "Name": "Name", "Docs": "", "Typewords": ["string"] }, { "Name": "UIDValidity", "Docs": "", "Typewords": ["uint32"] }, { "Name": "UIDNext", "Docs": "", "Typewords": ["UID"] }, { "Name": "Archive", "Docs": "", "Typewords": ["bool"] }, { "Name": "Draft", "Docs": "", "Typewords": ["bool"] }, { "Name": "Junk", "Docs": "", "Typewords": ["bool"] }, { "Name": "Sent", "Docs": "", "Typewords": ["bool"] }, { "Name": "Trash", "Docs": "", "Typewords": ["bool"] }, { "Name": "Keywords", "Docs": "", "Typewords": ["[]", "string"] }, { "Name": "HaveCounts", "Docs": "", "Typewords": ["bool"] }, { "Name": "Total", "Docs": "", "Typewords": ["int64"] }, { "Name": "Deleted", "Docs": "", "Typewords": ["int64"] }, { "Name": "Unread", "Docs": "", "Typewords": ["int64"] }, { "Name": "Unseen", "Docs": "", "Typewords": ["int64"] }, { "Name": "Size", "Docs": "", "Typewords": ["int64"] }] },
 		"RecipientSecurity": { "Name": "RecipientSecurity", "Docs": "", "Fields": [{ "Name": "STARTTLS", "Docs": "", "Typewords": ["SecurityResult"] }, { "Name": "MTASTS", "Docs": "", "Typewords": ["SecurityResult"] }, { "Name": "DNSSEC", "Docs": "", "Typewords": ["SecurityResult"] }, { "Name": "DANE", "Docs": "", "Typewords": ["SecurityResult"] }, { "Name": "RequireTLS", "Docs": "", "Typewords": ["SecurityResult"] }] },
-		"EventStart": { "Name": "EventStart", "Docs": "", "Fields": [{ "Name": "SSEID", "Docs": "", "Typewords": ["int64"] }, { "Name": "LoginAddress", "Docs": "", "Typewords": ["MessageAddress"] }, { "Name": "Addresses", "Docs": "", "Typewords": ["[]", "MessageAddress"] }, { "Name": "DomainAddressConfigs", "Docs": "", "Typewords": ["{}", "DomainAddressConfig"] }, { "Name": "MailboxName", "Docs": "", "Typewords": ["string"] }, { "Name": "Mailboxes", "Docs": "", "Typewords": ["[]", "Mailbox"] }, { "Name": "RejectsMailbox", "Docs": "", "Typewords": ["string"] }] },
+		"EventStart": { "Name": "EventStart", "Docs": "", "Fields": [{ "Name": "SSEID", "Docs": "", "Typewords": ["int64"] }, { "Name": "LoginAddress", "Docs": "", "Typewords": ["MessageAddress"] }, { "Name": "Addresses", "Docs": "", "Typewords": ["[]", "MessageAddress"] }, { "Name": "DomainAddressConfigs", "Docs": "", "Typewords": ["{}", "DomainAddressConfig"] }, { "Name": "MailboxName", "Docs": "", "Typewords": ["string"] }, { "Name": "Mailboxes", "Docs": "", "Typewords": ["[]", "Mailbox"] }, { "Name": "RejectsMailbox", "Docs": "", "Typewords": ["string"] }, { "Name": "Version", "Docs": "", "Typewords": ["string"] }] },
 		"DomainAddressConfig": { "Name": "DomainAddressConfig", "Docs": "", "Fields": [{ "Name": "LocalpartCatchallSeparator", "Docs": "", "Typewords": ["string"] }, { "Name": "LocalpartCaseSensitive", "Docs": "", "Typewords": ["bool"] }] },
 		"EventViewErr": { "Name": "EventViewErr", "Docs": "", "Fields": [{ "Name": "ViewID", "Docs": "", "Typewords": ["int64"] }, { "Name": "RequestID", "Docs": "", "Typewords": ["int64"] }, { "Name": "Err", "Docs": "", "Typewords": ["string"] }] },
 		"EventViewReset": { "Name": "EventViewReset", "Docs": "", "Fields": [{ "Name": "ViewID", "Docs": "", "Typewords": ["int64"] }, { "Name": "RequestID", "Docs": "", "Typewords": ["int64"] }] },
@@ -1215,6 +1215,8 @@ let loginAddress = null;
 let domainAddressConfigs = {};
 // Mailbox containing rejects.
 let rejectsMailbox = '';
+// Last known server version. For asking to reload.
+let moxVersion = '';
 const client = new api.Client();
 // Link returns a clickable link with rel="noopener noreferrer".
 const link = (href, anchorOpt) => dom.a(attr.href(href), attr.rel('noopener noreferrer'), attr.target('_blank'), anchorOpt || href);
@@ -3186,7 +3188,7 @@ const newMsglistView = (msgElem, listMailboxes, setLocationHash, otherMailbox, p
 		}
 	};
 	const cmdDelete = async () => {
-		if (!confirm('Are you sure you want to permanently delete?')) {
+		if (!window.confirm('Are you sure you want to permanently delete?')) {
 			return;
 		}
 		await withStatus('Permanently deleting messages', client.MessageDelete(mlv.selected().map(miv => miv.messageitem.Message.ID)));
@@ -5872,7 +5874,15 @@ const init = async () => {
 			}
 		};
 		eventSource.addEventListener('start', (e) => {
-			const start = checkParse(() => api.parser.EventStart(JSON.parse(e.data)));
+			const data = JSON.parse(e.data);
+			if (moxVersion && data.Version !== moxVersion) {
+				if (window.confirm('Server has been updated to a new version. Reload?')) {
+					window.location.reload();
+					return;
+				}
+			}
+			moxVersion = data.Version;
+			const start = checkParse(() => api.parser.EventStart(data));
 			log('event start', start);
 			connecting = false;
 			sseID = start.SSEID;
diff --git a/webmail/webmail.ts b/webmail/webmail.ts
index e77b56b..1f4bfe5 100644
--- a/webmail/webmail.ts
+++ b/webmail/webmail.ts
@@ -227,6 +227,9 @@ let domainAddressConfigs: {[domainASCII: string]: api.DomainAddressConfig} = {}
 // Mailbox containing rejects.
 let rejectsMailbox: string = ''
 
+// Last known server version. For asking to reload.
+let moxVersion: string = ''
+
 const client = new api.Client()
 
 // Link returns a clickable link with rel="noopener noreferrer".
@@ -2911,7 +2914,7 @@ const newMsglistView = (msgElem: HTMLElement, listMailboxes: listMailboxes, setL
 		}
 	}
 	const cmdDelete = async () => {
-		if (!confirm('Are you sure you want to permanently delete?')) {
+		if (!window.confirm('Are you sure you want to permanently delete?')) {
 			return
 		}
 		await withStatus('Permanently deleting messages', client.MessageDelete(mlv.selected().map(miv => miv.messageitem.Message.ID)))
@@ -6268,7 +6271,16 @@ const init = async () => {
 		}
 
 		eventSource.addEventListener('start', (e: MessageEvent) => {
-			const start = checkParse(() => api.parser.EventStart(JSON.parse(e.data)))
+			const data = JSON.parse(e.data)
+			if (moxVersion && data.Version !== moxVersion) {
+				if (window.confirm('Server has been updated to a new version. Reload?')) {
+					window.location.reload()
+					return
+				}
+			}
+			moxVersion = data.Version
+
+			const start = checkParse(() => api.parser.EventStart(data))
 			log('event start', start)
 
 			connecting = false