Unable to access mail since Thunderbird 78.4.0 update

Avast Free Antivirus / Premium Security
1

Last Saturday Thunderbird automatically updated to v78.4.0 and immediately I was unable to access emails from the servers (I have 3 accounts on different mail servers). Whenever I selected ‘Get Messages’ Thunderbird would indicate it was accessing a server but the process hung from there. There are no error messages, just no email.
After troubleshooting I have found that disabling Avast’s (v20.8.2432) Mail Shield allows Thunderbird to access and download emails normally so I am currently running with that shield disabled.I am running up to date Windows 10.

I have tried running Thunderbird in safe mode without addons, I have tweaked security.tls/version.min from 3 to 1 via about:config and have completely uninstalled/reinstalled Avast and installed Thunderbird 78.4.1 over the top. Since then I have updated Thunderbird to 78.4.2. None of these have made any difference.

The problem only occurs when the Avast Mail Shield is turned on.

Also, I tried to log a support ticket as I have had a paid subscription for almost a decade and so cannot find my order number - I assum the support ticket was lost because I did not get a confirmation. It seems I can’t access Avast Support without an order number … ridiculous!

2

Hello,

I’m afraid we’re several encountering this problem of non compatibility between last version of Thunderbird + gmail and Avast.
The only solution seems to deactivate the mail agent of Avast.
Will Avast try to implement a solution ?
Thanks
Best regards

3

Problem solved thanks to Jovan from Avast Support. I needed to follow the instructions from their official support page for importing the Mail Shield certificate into your mail client, as it should resolve this type of issue:

https://support.avast.com/en-my/article/Troubleshoot-invalid-email-certificate

4

Had the problem all of a sudden in TB 78.4.3 and had to deactivate the e-mail scanner.

An Avast update on Nov. 14 2020 has fixed it.

I didn’t get any certificate errors, just a ‘getting mail’ hang which could only be stopped by closing TB.