Optimise Gmail sync performance

A Gmail account can sync in one of two ways. The optimised way fills the list of a large mailbox in seconds and downloads the messages themselves several times faster. The fallback way does the same work, but takes minutes where the optimised way takes seconds. The app uses the optimised way whenever Gmail allows it, so for most accounts there is nothing to do.

Either way, your mail travels only between this device and Google, with the same sign-in.

Check which one your account uses

Open Settings, choose Accounts, then your Gmail account, and look for Sync technology.

• Optimised: the account syncs the fast way. There is nothing to change.
• Fallback: Gmail does not allow the fast way for this account, so the app uses the slower one. Your mail still syncs completely, and sending, labels, flags and everything else work as normal; only downloading takes longer.
• Can't connect: the network you are on blocks the way Gmail syncs, so no new mail arrives for now. The last section of this page explains it.

Just after the app opens, it may show Checking… for a moment while it finds out which way works.

A Fallback has one of two causes, and each has its own fix below.

All Mail is hidden in your Gmail settings

The fast way reads your mail through Gmail's All Mail folder. Gmail lets you hide that folder from mail apps, and while it is hidden, the app falls back.

To show it again, on a computer:

1. Open Gmail in a web browser.
2. Click the gear icon, then See all settings.
3. Open the Labels tab.
4. In the All Mail row, tick Show in IMAP.

Gmail saves the change straight away. Then restart the app, as described under "After changing a setting" below.

Your organisation has turned IMAP off

On a Google Workspace account (a work or school address that Google hosts for your organisation), your administrator decides whether mail apps may use IMAP, which is what the fast way relies on. If they have turned it off, the app falls back, and nothing in your own Gmail settings changes that.

Ask your administrator to allow IMAP for your account. In the Google Admin console it is under Apps, Google Workspace, Gmail, End User Access, as POP and IMAP access. If your organisation allows only a list of approved mail apps there, Allodia Mail & Calendar needs to be on that list.

After changing a setting

The app settles on a way to sync when it starts, so a change in Gmail takes effect the next time it opens. Close the app completely and open it again: on macOS, quit it from the menu bar; on iPhone and Android, swipe it away in the app switcher. Sync technology then shows Optimised.

The mail already on this device stays where it is. The app carries on from it rather than downloading everything again.

When it says "Can't connect"

Some networks, often in hotels, on guest Wi-Fi and at some workplaces, block the way Gmail syncs while letting the rest of the internet through. On such a network your Gmail mail cannot reach the app: no new mail arrives, and the account is marked as unable to reach its server.

Nothing is wrong with your account, and there is nothing to change in Gmail. The mail already on this device stays readable. As soon as you are on another network, such as your home Wi-Fi or mobile data, mail arrives again by itself and Sync technology goes back to Optimised. There is no need to restart the app.