IMAP timing out in Apple Mail in Big Sur

Hi,

I have been experiencing the same issue on my 2019 iMac.

O/S: Big Sur (11.0.1)

Anti-virus: Avast Security 14.6

Network monitor: Radio Silence 3.0 (Beta)

I have done some research and found the following page (Avast forums) which provides detailed explanations:

https://forum.avast.com/index.php?topic=239798.0

Running the command in Terminal (as instructed) did return both Radio Silence and Avast Antivirus as a source of issues.

Avast has reported the issue to Apple and I do hope they will address it in the upcoming 11.1 release. Avast is also working on some fix in the upcoming 14.7 release.

Meanwhile I have followed Avast's recommendation and disabled their Web Shield for now. Mail is back to normal while Radio Silence (currently in a beta release that is compatible with Big Sur) is running fine.

(@sketchywizard : You may want to restart your computer to test whether Avast + Little Snitch operate normally once Web Shield is disabled, that is exactly what I did and it did fix the issue. Maybe worth a try.)

Hope this helps.

I had the same problem on two Macs. I found that by deleting all network filters (Avast, Little Snitch) in the Network system preference, the problem immediately evaporated. Am still experimenting with various combinations of these because some seem to work on their own but not together...

Thank you so so very much. Have been tearing my hair out over this for a few weeks now. Turning off the Avast mail shield solved the problem. Hope there is a fix soon to ensure the protection mail shield offers.

THIS. I was running AVG virus scanner which Web & Email protection. Switching off the email protection immediately fixed the IMAP connection timeout problem.

I had the same problem with the mail app not connecting to gmail after the big sur install. I rebooted, that did nothing. I deleted the gmail accounts from the mail app and then reinstalled them, that did nothing. Then I uninstall Avast virus scanning and restarted - mail app now fine and connecting to gmail again nd receiving emails!

Seems to be a Big Sur Firewall issue. I have Apple Mail, Google (IMAP), and Comcast (IMAP). All incoming works fine, but outgoing SMTP for Google and Comcast would fail. I turned off the built-in Firewall and everything works fine now. I went back and turned Firewall back on and added an entry for Mail.app to allow all incoming connections - seems to work.

As others have mentioned, disabling ONLY the EMAIL SHIELD from AVG solved the problem of connectivity to IMAP. So you may want to try this or if you don't have AVG any similar application that may "interfere" with the connections.

For me I found a workaround.

Any app that uses System Extension which filters network connections seems to be a problem.

But mostly with Apple Mail. Some other clients may work.

https://forum.avast.com/index.php?topic=239798.0

So turn off Little Snitch, Avast anti Virus etc.

Yes, same here!

So who has to improve the service? AVG or Apple?

I wrote AVG already and they seem to be aware of the issue.

I had also problems to get connection to the internet with the AVG VPN Client.

Switched that off and it works fine again!

Little Snitch, after updating is no problem anymore!

Same problem here a couple of weeks later on Big Sur 11.0.1. Eternal beachball on sending gmail on both Mail and Mimestream. No problems sending via the Gmail web interface. Disabling Bitdefender protection seems to have caused this problem to go away, but that's not ideal.

Did you try explicitly adding Mail.app to Firewall Options?

fyi, Prior to Big Sur update I was using two different SSL check apps and had been using same for several years. After update, neither worked and I trashed both as a consequence. It is curious ... only haven't had time to consider all the changes ...