Troubleshooting
Gmail: “too many connections”
Gmail limits simultaneous connections per account. Here’s why Heron may say “The mail server is busy” and how to fix it.
Gmail only accepts a limited number of simultaneous IMAP connections for a given account, about 15. That limit is shared by every app and device reading the account over IMAP. Once it’s reached, Gmail refuses new connections.
What you see in Heron
An action (opening a message, moving, searching…) fails with:
The mail server is busy (too many open connections). Try again in a few seconds.
Heron already retries on its own several times before showing this message, and uses few connections per mailbox. If the error keeps coming back, another app is usually opening a lot of them.
How to fix it
- Wait a few seconds and try again: unused connections eventually close.
- Quit other mail apps reading this Gmail account over IMAP: Apple Mail, Outlook, Thunderbird, another app on your phone or another computer, an old client left open…
- Check the services connected to your Google account (email backups, automatic sorting tools, old devices): in your Google Account, Security → Your connections to third-party apps & services, remove the ones you no longer use.
- If it persists, reconnect the mailbox in Heron: Settings → the mailbox → Sign in again with Google.
Good to know: Gmail on the web and the official Gmail app don’t use IMAP: they don’t count toward this limit.
What about other providers?
Other services (iCloud, Yahoo, IMAP hosts) have limits too, often lower. The same tips apply. If a mailbox stays in error, see A mailbox shows an error.