Mail-Server Communication

[perfect-dark]

I'm using Thunderbird to access my eMails at posteo. Since today, Thunderbird cannot communicate with the Posteo-Server. I think it has something to do with the certificates. I tried this procedure, but it didn't work out so far:
https://support.avast.com/de-de/article/Troubleshoot-invalid-email-certificate/
When I turn off the Mail-Protection in avast, everything works fine.

Any suggestings how to solve this issue?

[DavidR]

Exactly what did you do in relation to the instructions.

Of course when you disable the Mail Shield it will work, the reason the security certificate is required is, Avast acts as an intermediary in order to collect your email and scan it before you receive it.

See this post https://forum.avast.com/index.php?topic=260178.msg1600393#msg1600393 I did a while ago about this and follow the topic from there, does that help ?

[perfect-dark]

what I did was to export the certificate from avast and import it to thunderbird - exactly as described in the help section from avast. That's not helping.

One interesting thing: when I disable the mail-protection once, check my mails, then again, turn on the protection, checking mails is still possible for some time. Really strange...