Folks - I found one other forum thread relating to AVG interfering with T-bird:
https://support.avg.com/answers?id=9060N000000g7oEQAQ
... but it's not quite my problem. Generally, I can get small text-only emails through T-bird with AVG AV on. However for awhile now, I have been having consistent problems with file with attachments 3mg +/- or greater size choking trying to copy the email to the provider Send folder and/or Drafts folder...it varies. The provider is a German/Danish outfit, Posteo.net, which has been working fine for my girlfriend for quite awhile, and me generally. When I send above-size files with attachments or graphics directly through their web interface, no issues, they go right through. I verified with Posteo that the T-bird server settings were right, they confirmed they were, but said that anti-virus programs could mess with sending/copying, etc, so I turned of AVG AV and tried resending an email that had just choked this way (6.5mg) and sure enough, it went right through T-bird. So I'm suspecting. Can you all take a look at what this might be? I'm not getting any messages from AVG that the mails are a threat or something like that. I can leave AVG off and just use the Windows 10 firewall of course, but I like the AVG features and info feedback. Thanks in advance.
Hi Jack.
We'll certainly look into this. To further narrow down the issue, we'd request to disable individual components in AVG AntiVirus free and try to send the email. Click this link for instructions to disable individual components.
I appreciate your efforts in trying to resolve this issue, Jack.
I have sent an email to provide additional support. Please check the email and follow the instructions.
Hi Jack.
We'll certainly look into this. To further narrow down the issue, we'd request to disable individual components in AVG AntiVirus free and try to send the email. Click this link for instructions to disable individual components.