There is no risk at all as long as your anti-virus on-access scanner works and has up to date definitions. Thunderbird does not carry out Javascript code in emails. A malicious attachment sitting in an email message does no harm as long as you don't open it or deliberately decide to run it. Use your brain. If something looks suspicious, be careful. In addition, new types of malware attached to an email often aren't recognized by anti-virus scanners anyway, because no definition exists yet. So the security anti-virus vendors promise is very fragile at best. What's completely ridiculous is scanning attachments in outgoing messages.

Thank you christ1 for taking the time to explain this.

Unfortunately the problem has returned despite having discontinued the anti-virus scanning.

Create an exception in your anti-virus software for the Thunderbird profile folder, so that the anti-virus real-time scanner will not scan it.

Don't let your anti-virus software scan incoming and outgoing messages.

Don't let your anti-virus software scan attachments.

Don't let your anti-virus software intercept your secure connection to the server.

Remove any add-ons your anti-virus software may have installed in Thunderbird.

Reducing security thresholds hardly seems like an appropriate remedy.

This suggestion brings back memories from the distant past. I ask the IT geniuses to work on reducing the reported errors in a project. The next error report went down to 2 pages from 25 pages before.

When I asked how they did it they said they just reduced the rejection criteria.

Gotta love techies.

jsbsjsbs said

Reducing security thresholds hardly seems like an appropriate remedy. ... When I asked how they did it they said they just reduced the rejection criteria. Gotta love techies.

Unfortuntely you have added nothing useful ot this topic.

Hi Marti. I just found your last posting here.

History - in https://support.mozilla.org/en-US/questions/996264?page=2#answer-630304 you wrote you changed from McAfee to Trend. And in https://support.mozilla.org/en-US/questions/1076754#answer-810648 you wrote that running ccleaner solved your problem. And apparently your problem has returned since you ran ccleaner.

And it sounds like you changed from Trend to Avast??

> the warnings that I am putting my self at risk are daunting. It has never made sense to me that we would be advised to turn off what seems to be such an important function of anti-virus software.

Ignore them - the AV vendors would like you to think these features in indespensible. But these features are a pain in the butt and a source of many problems encountered by email users.

christ1's advice is solid. How are you doing since he posted??