With offline support, you can use the Fastmail mobile app or web interface even if you're not connected to the Internet. You can view and edit your mail, contacts, and calendars, and even reply to messages or make changes to your settings — any changes you make will be synced as soon as you're back online.
If you'd like to be able to access your mail while offline, you will first need to enable offline support for your device or browser (see Enable offline support below).
If you do not have offline support enabled, it is expected behavior to see a "Could not connect to server" banner over a loading screen when attempting to access Fastmail offline.
Enable offline support
You can enable offline support for your device by going to Settings → Offline and clicking the toggle button next to Enable offline support.
We'll start downloading mail to your device so that it can be available for offline access. You can choose whether you'd like us to cache only recent mail (any message that has previously been viewed on this device, plus any future messages you receive) or if you'd like us to cache all mail (every message that's in your account).
The mobile app will need to stay open and active (not running in the background) while the device is syncing. Syncing on your browser can happen in the background.
Note: If you see a banner on the Settings → Offline screen that says "Long-term session required," this means that you will need to log out, then log back in with the Keep me logged in option enabled. Once you are logged in with Keep me logged in selected, you should then be able to return to the Settings → Offline screen and enable offline support.
Disable offline support
You can disable offline support for your device by going to Settings → Offline and clicking the toggle button next to Disable offline support, then selecting Confirm.
Disabling offline support will remove the cached data that we previously downloaded to your device while offline support was enabled.
Limitations
While offline, certain features may not be available or may behave differently.
Mail search
Mail search will only work on messages that have been cached offline.
Mail search cannot search inside attachments while offline.
Stemming is not used to match phrases while offline, which means that we won't automatically include plurals (fox, foxes) and tenses (fish, fishing, fished) in search results as we normally would. Offline mail search will instead use prefix matching, which means that when you search for a phrase, we will include any words that include that phrase at the beginning (e.g., searching fox would match "fox", "foxes", "foxtrot", etc.).
Snoozed mail
If you're offline when a snoozed message is scheduled to return to your Inbox, you will not see the snoozed message reappear until you're back online.
Calendar reminders
You will not receive calendar reminder notifications while offline.
Attachments
Attachments are only cached for offline use when opened on the device.
Attachments cannot be deleted from messages while offline.
Account, billing, and security settings
You cannot make the following changes to your Fastmail account while offline:
- Add, edit, or delete users
- Add, edit, or delete custom domains
- Make changes to your subscription plan
- Update your billing details
- Change any security-related settings
Additional reading
If you're interested in the technical behind-the-scenes work that went into introducing offline support, check out our Fastmail Advent 2024 blog posts on the topic: