Fastmail seems to be struggling

jlyman · February 9, 2026, 3:03am

Problem

Since the last update or two my Fastmail account seems to not be syncing read or archived statuses well at all. I’ll read and archive emails from my Fastmail account either on my phone or directly on the Fastmail website, and return to Mailspring where it never updates the status for unread messages.

I’ve tried:

waiting a long time (a day)
manually syncing (F5)
closing and reopening Mailspring
removing and re-adding the account.

If I take a message that has been read and archived elsewhere but is still showing up as visible in the inbox and unread in Mailspring, I can read it and archive it, and it will go away. But it really doesn’t want to update messages without manual interaction from me.

Note: new messages are coming in just fine, so it is definitely syncing new items. Just existing ones that have been interacted with on other platforms it is not updating.

Context

All my other accounts (Gmail, MS) seem fine, just Fastmail is having issues.

I don’t see anything in particular in the logs for this account. Attaching a recent (sanitized) version of the sync log at the end of this post, in case it reveals anything interesting.

Email Provider

Fastmail

Setup

OS and Version: macOS 15.7.1
- Installation Method: Download and extract to /Applications
Mailspring Version: 1.17.3 (I think this was happening on the immediately previous version too, I’ve been seeing it for about a week).
Mailspring Pro subscription

Recent sync log (they all look like this):

25685 [2026-02-08 20:58:06.575] [background] [info] Syncing folder list...
25685 [2026-02-08 20:58:06.688] [background] [info] syncFolderChangesViaCondstore - INBOX: modseq 854991 to 854991, uidnext 28938 to 28938
25685 [2026-02-08 20:58:06.738] [background] [info] syncFolderChangesViaCondstore - Sent: modseq 854722 to 854722, uidnext 9680 to 9680
25685 [2026-02-08 20:58:06.825] [background] [info] syncFolderChangesViaCondstore - Drafts: modseq 854724 to 854724, uidnext 1814 to 1814
25685 [2026-02-08 20:58:06.871] [background] [info] syncFolderChangesViaCondstore - Archive: modseq 854990 to 854990, uidnext 125313 to 125313
25685 [2026-02-08 20:58:07.189] [background] [info] syncFolderChangesViaCondstore - Trash: modseq 854480 to 854480, uidnext 186 to 186
25685 [2026-02-08 20:58:07.235] [background] [info] syncFolderChangesViaCondstore - Spam: modseq 854106 to 854106, uidnext 294 to 294
25685 [2026-02-08 20:58:07.281] [background] [info] syncFolderChangesViaCondstore - Mailspring: modseq 497111 to 497111, uidnext 1 to 1
25685 [2026-02-08 20:58:07.327] [background] [info] syncFolderChangesViaCondstore - ###: modseq 746293 to 746293, uidnext 3 to 3
25685 [2026-02-08 20:58:07.373] [background] [info] syncFolderChangesViaCondstore - ###: modseq 746304 to 746304, uidnext 12 to 12
25685 [2026-02-08 20:58:07.419] [background] [info] syncFolderChangesViaCondstore - ###: modseq 746305 to 746305, uidnext 2 to 2
25685 [2026-02-08 20:58:07.465] [background] [info] syncFolderChangesViaCondstore - ###: modseq 746345 to 746345, uidnext 41 to 41
25685 [2026-02-08 20:58:07.514] [background] [info] syncFolderChangesViaCondstore - ###: modseq 749112 to 749112, uidnext 2768 to 2768
25685 [2026-02-08 20:58:07.582] [background] [info] syncFolderChangesViaCondstore - ###: modseq 839865 to 839865, uidnext 28716 to 28716
25685 [2026-02-08 20:58:07.679] [background] [info] syncFolderChangesViaCondstore - ###: modseq 806654 to 806654, uidnext 113 to 113
25685 [2026-02-08 20:58:07.725] [background] [info] syncFolderChangesViaCondstore - ###: modseq 497110 to 497110, uidnext 145 to 145
25685 [2026-02-08 20:58:07.771] [background] [info] syncFolderChangesViaCondstore - ###: modseq 746291 to 746291, uidnext 76 to 76
25685 [2026-02-08 20:58:07.819] [background] [info] syncFolderChangesViaCondstore - ###: modseq 853729 to 853729, uidnext 34 to 34
25685 [2026-02-08 20:58:07.865] [background] [info] syncFolderChangesViaCondstore - ###: modseq 497113 to 497113, uidnext 1 to 1
25685 [2026-02-08 20:58:07.911] [background] [info] syncFolderChangesViaCondstore - ###: modseq 806661 to 806661, uidnext 4 to 4
25685 [2026-02-08 20:58:07.957] [background] [info] syncFolderChangesViaCondstore - ###: modseq 806768 to 806768, uidnext 108 to 108
25685 [2026-02-08 20:58:08.005] [background] [info] syncFolderChangesViaCondstore - ###: modseq 806832 to 806832, uidnext 65 to 65
25685 [2026-02-08 20:58:08.053] [background] [info] syncFolderChangesViaCondstore - ###: modseq 806969 to 806969, uidnext 140 to 140
25685 [2026-02-08 20:58:08.104] [background] [info] syncFolderChangesViaCondstore - ###: modseq 746216 to 746216, uidnext 516 to 516
25685 [2026-02-08 20:58:08.168] [background] [info] syncFolderChangesViaCondstore - ###: modseq 853821 to 853821, uidnext 63 to 63
25685 [2026-02-08 20:58:08.215] [background] [info] syncFolderChangesViaCondstore - ###: modseq 839630 to 839630, uidnext 21 to 21
25685 [2026-02-08 20:58:08.261] [background] [info] syncFolderChangesViaCondstore - ###: modseq 497121 to 497121, uidnext 2 to 2
25685 [2026-02-08 20:58:08.307] [background] [info] syncFolderChangesViaCondstore - ###: modseq 838912 to 838912, uidnext 3811 to 3811
25685 [2026-02-08 20:58:08.376] [background] [info] syncFolderChangesViaCondstore - ###: modseq 852531 to 852531, uidnext 38 to 38
25685 [2026-02-08 20:58:08.422] [background] [info] syncFolderChangesViaCondstore - ###: modseq 825710 to 825710, uidnext 113 to 113
25685 [2026-02-08 20:58:08.470] [background] [info] syncFolderChangesViaCondstore - ###: modseq 825730 to 825730, uidnext 21 to 21
25685 [2026-02-08 20:58:08.472] [background] [info] Sync loop deleting unlinked messages with phase 2.
25685 [2026-02-08 20:58:08.482] [background] [info] Sync loop complete.

bengotow · February 11, 2026, 5:46pm

Hey Joshua - thanks for reporting this. I really appreciate the detailed logs. We just released an update to Mailspring (1.17.4) with a few sync-related fixes, but reading this again I don’t know if it will address the problems you’re running into. I’ll investigate this and see if I can reproduce the problem. We did make a change to help iCloud accounts sync deterministically when the same message appears in multiple folders, but I don’t think that would have caused this.

jlyman · February 11, 2026, 10:56pm

Thanks Ben for checking in! I’m still seeing the same behavior with the new version. Here’s a better set of logs that pinpoints the behavior for just one message. I’d guess that the key message in my issue here is the following, found near the end of the logs:

Message nEd6vqMPnChVHLYNEtPc7pEv4gF3joQ8x5kToQcBU staying in FTtfgpFtMJjoihxLv1b6xprMUM8SBepmBLNxp44rF (priority 0), ignoring 8sLfVeztr1qcUEwxFcM1KGsDN9df7QkxnvouNpiQk (priority 4)

The specific message with ID nEd6vqMPnChVHLYNEtPc7pEv4gF3joQ8x5kToQcBU gets received, read status updated, and then it looks like it notices that something changed about it’s location, but from my opaque read of it looks like it doesn’t change it because of… reasons.

Here are the full logs for this interaction:

// Email received at 16:42, appears here as message ID nEd6vqMPnChVHLYNEtPc7pEv4gF3joQ8x5kToQcBU

1686 [2026-02-11 16:42:51.998] [foreground] [info] Idle exited with code 0
1686 [2026-02-11 16:42:52.048] [foreground] [info] syncFolderChangesViaCondstore - INBOX: modseq 855544 to 855547, uidnext 29020 to 29021
1686 [2026-02-11 16:42:52.094] [foreground] [info] syncFolderChangesViaCondstore - Changes since HMODSEQ 855544: 1 changed, 0 vanished
1686 [2026-02-11 16:42:52.277] [foreground] [info] Idling on folder INBOX
1686 [2026-02-11 16:43:05.075] [background] [info] Syncing folder list...
1686 [2026-02-11 16:43:05.177] [background] [info] syncFolderChangesViaCondstore - INBOX: modseq 855547 to 855547, uidnext 29021 to 29021
1686 [2026-02-11 16:43:05.227] [background] [info] syncFolderChangesViaCondstore - Sent: modseq 855466 to 855466, uidnext 9681 to 9681
1686 [2026-02-11 16:43:05.276] [background] [info] syncFolderChangesViaCondstore - Drafts: modseq 854724 to 854724, uidnext 1814 to 1814
1686 [2026-02-11 16:43:05.323] [background] [info] syncFolderChangesViaCondstore - Archive: modseq 855544 to 855544, uidnext 125401 to 125401
1686 [2026-02-11 16:43:05.400] [background] [info] syncFolderChangesViaCondstore - Trash: modseq 854480 to 854480, uidnext 186 to 186
1686 [2026-02-11 16:43:05.448] [background] [info] syncFolderChangesViaCondstore - Spam: modseq 855540 to 855540, uidnext 296 to 296
1686 [2026-02-11 16:43:05.496] [background] [info] syncFolderChangesViaCondstore - Mailspring: modseq 497111 to 497111, uidnext 1 to 1
1686 [2026-02-11 16:43:06.710] [background] [info] Sync loop deleting unlinked messages with phase 2.
1686 [2026-02-11 16:43:06.712] [background] [info] Sync loop complete.

...
// Email marked as read in Fastmail web client, not archived
...

1686 [2026-02-11 16:44:52.458] [foreground] [info] Idle exited with code 0
1686 [2026-02-11 16:44:52.523] [foreground] [info] syncFolderChangesViaCondstore - INBOX: modseq 855547 to 855548, uidnext 29021 to 29021
1686 [2026-02-11 16:44:52.570] [foreground] [info] syncFolderChangesViaCondstore - Changes since HMODSEQ 855547: 1 changed, 0 vanished
1686 [2026-02-11 16:44:52.570] [foreground] [info] - Updating message nEd6vqMPnChVHLYNEtPc7pEv4gF3joQ8x5kToQcBU
1686 [2026-02-11 16:44:52.570] [foreground] [info] -- Unread (true to false)
1686 [2026-02-11 16:44:52.578] [foreground] [info] Idling on folder INBOX

...
// Email gets successfully shown as Read in Mailspring
// Archive the message in Fastmail web client
...

1686 [2026-02-11 16:44:52.578] [foreground] [info] Idling on folder INBOX
1686 [2026-02-11 16:45:06.717] [background] [info] Syncing folder list...
1686 [2026-02-11 16:45:06.819] [background] [info] syncFolderChangesViaCondstore - INBOX: modseq 855548 to 855548, uidnext 29021 to 29021
1686 [2026-02-11 16:45:06.869] [background] [info] syncFolderChangesViaCondstore - Sent: modseq 855466 to 855466, uidnext 9681 to 9681
1686 [2026-02-11 16:45:06.922] [background] [info] syncFolderChangesViaCondstore - Drafts: modseq 854724 to 854724, uidnext 1814 to 1814
1686 [2026-02-11 16:45:06.969] [background] [info] syncFolderChangesViaCondstore - Archive: modseq 855544 to 855544, uidnext 125401 to 125401
1686 [2026-02-11 16:45:07.063] [background] [info] syncFolderChangesViaCondstore - Trash: modseq 854480 to 854480, uidnext 186 to 186
1686 [2026-02-11 16:45:07.112] [background] [info] syncFolderChangesViaCondstore - Spam: modseq 855540 to 855540, uidnext 296 to 296
1686 [2026-02-11 16:45:07.159] [background] [info] syncFolderChangesViaCondstore - Mailspring: modseq 497111 to 497111, uidnext 1 to 1
1686 [2026-02-11 16:45:08.277] [background] [info] Sync loop deleting unlinked messages with phase 1.
1686 [2026-02-11 16:45:08.283] [background] [info] Sync loop complete.
1686 [2026-02-11 16:45:52.729] [foreground] [info] Idle exited with code 0
1686 [2026-02-11 16:45:52.778] [foreground] [info] syncFolderChangesViaCondstore - INBOX: modseq 855548 to 855551, uidnext 29021 to 29021
1686 [2026-02-11 16:45:52.826] [foreground] [info] syncFolderChangesViaCondstore - Changes since HMODSEQ 855548: 0 changed, 0 vanished
1686 [2026-02-11 16:45:52.829] [foreground] [info] Idling on folder INBOX

...
// Message still showing up in Inbox in Mailspring
...

1686 [2026-02-11 16:47:08.287] [background] [info] Syncing folder list...
1686 [2026-02-11 16:47:08.388] [background] [info] syncFolderChangesViaCondstore - INBOX: modseq 855551 to 855551, uidnext 29021 to 29021
1686 [2026-02-11 16:47:08.436] [background] [info] syncFolderChangesViaCondstore - Sent: modseq 855466 to 855466, uidnext 9681 to 9681
1686 [2026-02-11 16:47:08.490] [background] [info] syncFolderChangesViaCondstore - Drafts: modseq 854724 to 854724, uidnext 1814 to 1814
1686 [2026-02-11 16:47:08.551] [background] [info] syncFolderChangesViaCondstore - Archive: modseq 855544 to 855551, uidnext 125401 to 125402
1686 [2026-02-11 16:47:08.679] [background] [info] syncFolderChangesViaCondstore - Changes since HMODSEQ 855544: 1 changed, 0 vanished
1686 [2026-02-11 16:47:08.680] [background] [info] - Message nEd6vqMPnChVHLYNEtPc7pEv4gF3joQ8x5kToQcBU staying in FTtfgpFtMJjoihxLv1b6xprMUM8SBepmBLNxp44rF (priority 0), ignoring 8sLfVeztr1qcUEwxFcM1KGsDN9df7QkxnvouNpiQk (priority 4)
1686 [2026-02-11 16:47:08.763] [background] [info] syncFolderChangesViaCondstore - Trash: modseq 854480 to 854480, uidnext 186 to 186
1686 [2026-02-11 16:47:08.812] [background] [info] syncFolderChangesViaCondstore - Spam: modseq 855540 to 855540, uidnext 296 to 296
1686 [2026-02-11 16:47:08.860] [background] [info] syncFolderChangesViaCondstore - Mailspring: modseq 497111 to 497111, uidnext 1 to 1
1686 [2026-02-11 16:47:09.970] [background] [info] Sync loop deleting unlinked messages with phase 2.
1686 [2026-02-11 16:47:09.975] [background] [info] Sync loop complete.
1686 [2026-02-11 16:47:31.939] [metadata] [info] Metadata delta stream closed.
1686 [2026-02-11 16:47:31.943] [metadata] [info] Metadata delta stream starting...

...
// Message mentioned, but didn't move in Mailspring
// Finally, in Mailspring I clicked on the message to view it and then archived it
...

1686 [2026-02-11 16:54:42.524] [main] [info] [local-222d1eb9-7c5b] Running ChangeFolderTask performLocal:
1686 [2026-02-11 16:54:42.538] [main] [info] [local-222d1eb9-7c5b] -- Succeeded. Changing status to `remote`
1686 [2026-02-11 16:54:42.890] [foreground] [info] Idle exited with code 0
1686 [2026-02-11 16:54:42.905] [foreground] [info] [local-222d1eb9-7c5b] Running ChangeFolderTask performRemote:
1686 [2026-02-11 16:54:43.130] [foreground] [info] [local-222d1eb9-7c5b] -- Succeeded. Changing status to `complete`
1686 [2026-02-11 16:54:43.177] [foreground] [info] syncFolderChangesViaCondstore - INBOX: modseq 855554 to 855554, uidnext 29022 to 29022
1686 [2026-02-11 16:54:43.179] [foreground] [info] Idling on folder INBOX
1686 [2026-02-11 16:54:43.191] [main] [info] [local-cb6a521f-a1ae] Running ChangeUnreadTask performLocal:
1686 [2026-02-11 16:54:43.197] [main] [info] [local-cb6a521f-a1ae] -- Succeeded. Changing status to `remote`
1686 [2026-02-11 16:54:43.547] [foreground] [info] Idle exited with code 0
1686 [2026-02-11 16:54:43.549] [foreground] [info] [local-cb6a521f-a1ae] Running ChangeUnreadTask performRemote:
1686 [2026-02-11 16:54:43.599] [foreground] [info] [local-cb6a521f-a1ae] -- Succeeded. Changing status to `complete`
1686 [2026-02-11 16:54:43.646] [foreground] [info] syncFolderChangesViaCondstore - INBOX: modseq 855554 to 855555, uidnext 29022 to 29022
1686 [2026-02-11 16:54:43.692] [foreground] [info] syncFolderChangesViaCondstore - Changes since HMODSEQ 855554: 1 changed, 0 vanished
1686 [2026-02-11 16:54:43.694] [foreground] [info] Idling on folder INBOX

jlyman · February 20, 2026, 3:34pm

Any potential update on this issue? I’m still needing to double-archive messages that I had archived on different clients.

bengotow · February 23, 2026, 3:04pm

Hey @jlyman - Mailspring 1.18.0 includes a fix in the sync engine for processing VANISHED notifications sent during IMAP IDLE (mailsync@5a31251). FastMail sends these notifications when messages are archived or moved, and Mailspring was previously expecting that it could ask for the notifications again later during sync, which FastMail does not support. This explains why read/archive state changes made elsewhere weren’t being reflected.

This release also fixes folder priority logic that was incorrectly being applied to non-iCloud accounts (mailsync@b7d0a7e), which may have contributed to the “Message staying in [folder], ignoring [archive]” behavior you observed in your logs.

I tested on a FastMail account and I think it’s working properly now - Update via snap refresh mailspring, the built-in auto-updater, or from https://www.getmailspring.com/download. Please let us know if the sync behavior improves with 1.18.0.

jlyman · February 23, 2026, 4:05pm

Oh yay, fantastic! Thanks Ben. I’ll update and test it out now/over the course of the day.

jlyman · March 1, 2026, 12:56pm

The new version has addressed the issue. Thanks so much!!