Foundry376/Mailspring 1.26.0

on GitHub

1.26.0 (10/1/2026)

This is a major sync reliability release - The sync engine now tracks every folder a message lives in, rather than forcing each message into a single folder. This permanently fixes mail "flickering" between folders or disappearing from the Inbox when the same message exists in two places — a long-standing issue for iCloud users, self-addressed mail that lands in both Inbox and Sent, Exchange's duplicate Sent copies, and ProtonMail labels. (#2891) This refactor was enabled by a huge new suite of automated mailsync tests that run against real Dovecot, Cyrus in Docker and fake problematic IMAP servers.

Features:

• Folder and unread counts left wrong by previous versions are repaired automatically on upgrade. Thanks @dansleboby!
• Calendars now refresh every 15 minutes instead of every 45, so invitations accepted on another device or meetings moved by the organizer show up sooner. Contacts sync slightly less often to conserve Google API quota. Thanks @brhellman!
• After an event is saved or deleted, Mailspring re-reads the calendar from the server so the event reflects what the server actually stored. (#2915) Thanks @brhellman!
• Calendars deleted or unshared on the server are now removed from Mailspring along with their events. Thanks @brhellman!
• Mailspring now records whether each calendar is your own or shared with you, so RSVPs are never written onto someone else's calendar. (#2916) Thanks @brhellman!
• Day and week calendar views now draw events with the same chip style as the month view, and selected events fill with the calendar's own color. (#2895) Thanks @manilabui!

Security:

• Links in print preview, quick-preview and "show original" windows now open in your browser instead of loading the remote page in the window.
• Links from auxiliary windows only open in your browser after a real click or keypress, so a meta refresh in a message can no longer open a page on its own.
• "Show All" on a clipped message now sanitizes the message body and blocks remote images like the reading pane.
• Replying, forwarding and sending no longer fetch remote images referenced by the message when automatic image loading is off. Opening an event's notes no longer fetches images referenced by its description, which could tell the sender you opened the invitation. (#2901) Thanks @brhellman!
• A malicious event UID can no longer cause the sync engine to write outside the calendar collection on the CalDAV server. Thanks @brhellman!

Bug Fixes:

• Fixed duplicate Sent copies appearing on Exchange Online, Gmail, Yahoo and Zoho, which file their own copy of sent mail.
• On servers without IMAP MOVE, moving a message no longer permanently erases other messages another client had only marked for deletion (e.g. Outlook's "mark for deletion" mode).
• Fixed several provider quirks: folder roles detected by name and \Archive support, servers reporting UIDNEXT 0, Coremail/NetEase servers that require an ID command, and servers that refuse LIST being treated as missing folders.
• Fixed mail rules not applying to self-addressed messages whose Inbox copy arrived after the Sent copy.
• Fixed the Unread view's recently-read threads leaking across views. (#2905) Thanks @dansleboby!
• Fixed Gmail messages losing text the sender placed inside the signature block when there was no quoted text. (#2902) Thanks @dansleboby!
• On Linux, fixed two title bars appearing on KDE and GNOME for users who never chose a menubar style. (#2903) Thanks @dansleboby!
• Fixed blank lines appearing in the inline reply composer. (#2896) Thanks @arnonuem!
• Fixed adding some Google Workspace and Office 365 accounts by always using the provider's servers for OAuth accounts. (#2907) Thanks @Jorl17!
• Fixed the Send button silently doing nothing when a draft's From address matches no account or alias; Mailspring now explains the problem. (#2910)
• Carriage returns are stripped from text dropped into the composer. (#2908)
• Fixed Google contacts with a birthday but no date failing to open in the contact editor. (#2912)
• Fixed an error when a sound effect can't be decoded. (#2911)
• Malformed URLs passed to Mailspring on launch are now ignored. (#2913)
• On macOS 27, notifications now respect the system "Play sound for notifications" setting and Focus modes, and the notification sound plays correctly.
• On macOS, fixed the window not being draggable beneath the window controls.
• Updated Electron to 44.5.1 to fix webview detach errors. (#2909)
• Mailspring now tells you when the server rejects an event save instead of leaving the unsaved edit on screen. (#2914) Thanks @brhellman!
• Fixed RSVPs to recurring events including other guests' attendance in the replies for moved or modified occurrences. (#2917) Thanks @brhellman!
• Fixed recurring events created in winter showing an hour off in summer: VTIMEZONEs now carry the zone's daylight saving rules, including every offset change. (#2885, #2900) Thanks @brhellman!
• Fixed Outlook and Exchange events using Windows zone names ("Central Standard Time") being shifted to your machine's time zone when edited. (#2897) Thanks @brhellman!
• Fixed an invitation that redefines the UTC zone shifting every UTC time for the rest of the session. (#2898) Thanks @brhellman!
• Fixed UTC timestamps in calendar data being read as local time. Thanks @brhellman!
• Fixed deleting a single occurrence of a recurring event deleting the entire series on the server. Thanks @brhellman!
• Fixed accepting an invitation already present on the calendar failing as a duplicate create. Thanks @brhellman!
• Fixed every calendar being marked read-only on servers that omit or aggregate privilege information. Thanks @brhellman!
• Fixed Fastmail/Cyrus scheduling Inbox and Outbox collections appearing as calendars, and DAV principal discovery on some servers. Thanks @brhellman!
• Fixed RSVP emails violating MIME line-length and encoding rules, which some mail servers refuse. Mailspring also accepts iTIP COUNTER proposals when responding. Thanks @brhellman!
• Fixed a failing manual calendar refresh aborting the sync process. Thanks @brhellman!
• Fixed CalDAV and CardDAV discovery on servers that use 303, 307 or 308 redirects from /.well-known. Thanks @Alintya!
• Fixed a blur on a calendar time field moving the event to today, a timed event losing its time when its day is changed, and a bare hour like "3" always being read as PM. (#2890, #2892, #2893) Thanks @manilabui!
• Fixed all-day event saves writing the wrong date span. (#2894) Thanks @manilabui!
• Fixed event notes missing when the description begins with itemprop=description meta tags.

Improvements:

• The offline indicator is a less aggressive gray, and coming back online re-syncs your accounts immediately, clearing the indicator.

Developer:

• Added an extensive fakeimap, Cyrus and Dovecot test suite for the sync engine.
• Updated out of date GitHub Actions versions.
• Fixed Playwright assertions for the macOS 27 navigation bar.