Avast blocks mail access in Thunderbird

General Topics
1

I have an active Avast free anti-virus (program build 12.3.3154.0, definitions 160822-1) installed on a laptop running Windows 10 Pro X64.

Recently, I could not receive or send e-mails in Thunderbird 45.2.0 any more. No changes to the installation, except for the automatic updates of Windows & Avast. I update Thunderbird manually after an alert of a new version. It seems that the problem must be caused by an automatic update that changed a setting on the PC or a virus.

I then checked for malware on the system despite active shields in place. I ran a full scan and also used another malware scanner to scan the computer. No problems reported. I then suspected Thunderbird. I uninstalled it and download a fresh copy and install it. I could not set up the accounts as Thunderbird’s wizard reported problems when verifying the user name and password for GMail and Yahoo accounts.

After I installed Opera Mail and landed with the same problem, I realise that the problem is most likely with the firewall blocking access.

After installing Thunderbird again, I disabled the mail shield in Avast for 10 minutes and tried to set up the accounts again. It worked fine. I could send and receive messages. When I switch the mail shield in Avast on again, no e-mails in or out.

I added Thunderbird to the allowed programs/apps in Windows firewall and I checked that the Avast SSL certificate appears in the certificate list of Thunderbird. I also verified that ports 993 and 465 are in the list of mail ports in Avast troubleshooting section. This did not solve the problem.

The only options I currently seem to have is:

  1. Turn mail shield of permanently - not acceptable
  2. Get another anti-virus - I have the same setup running on my desktop PC with another anti-virus and there are no mail problems.

Any suggestions?

2

First thing to do is installing the latest avast version.
Best is to perform a clean installation.

3

I already checked for the latest update to both the program and the definitions.

4

See if that helps: https://www.avast.com/faq.php?article=AVKB91#artTitle

5

When I realised that the problem is linked to Avast, I uninstalled Avast and re-installed Avast from a new download. Then I verified that the copies are the latest available.

I also came across the page you referred to and followed the steps to export the Avast certificate and imported it into Thunderbird; actually, I deleted the certificate that was already in Thunderbird and imported the one I exported from Avast. Then I enabled the mail shield and try to send a test message; it did not send. When I disabled the mail shield again and re-send the test message, it went through without a problem.

6

Sorry, no idea then…
Best you contact support: https://support.avast.com/support/tickets/new

7

Thank you for the help. It seems to be an unusual case that other users are not familiar with.

I am logging it with Avast support.

8

OK, you’re welcome.