What is your problem in the first place?

I want to view an archived email, did my post not show? I'll repeat it below. Cheers

Hi, can anyone tell me if it is possible to view archived emails in Thunderbird. If so how? I'm using Windows 10 and Thunderbird version is 78.8.0 Thanks.

Did you archive within TB or export mail outside of TB, and in what format?

I just clicked on 'accept' when Thunderbird asked me if I wanted to save space by archiving emails, It does that from time to time. So I imagine that they are archived in Thunderbird, I haven't exported them anywhere.

I've never heard of TB asking to archive mail automatically, so I wonder if this provided by an add-on or 3rd-party app.

Ah ok thanks, don't know about that, maybe I misunderstood the message in the thunderbird app, maybe it said compress or delete instead of archive :-/

TB does compact folders automatically, and issues a prompt, but the purpose is to free up space by permanently removing deleted messages from the profile:

http://kb.mozillazine.org/Compacting_folders

Ok thanks, my bad.