This is a big issue for me too.
I've noticed that email from Microsoft exchange servers seems to default to +0000, whereas it should have been customized to where the Microsoft exchange server actually is (+1200 in my case).
Thunderbird then faithfully uses the original time zone on the forwarded email.
That is the sender's fault. Or rather the fault of whoever set up their server.
But it becomes the Thunderbird user's problem.
I want to say it affects about 80% of the email I receive from the corporate email addresses I correspond with. And it does get really confusing.
Even if we shouldn't have to work around someone else's fault in failing to update their own server settings, it's just not practical to wait on them to sort themselves out.
So, it would be nice if Thunderbird allowed users an option to show the time of the forwarded email in the Thunderbird user's time zone.
I'm not aware of any other mail program that respects the sender's original time zone in the way that Thunderbird currently does. Other programs do seem to just convert it to the local time zone.
I can see that this issue has come up a few times before, and it would be awesome if it could be dealt with e.g.
https://support.mozilla.org/en-US/questions/1352676
https://support.mozilla.org/en-US/questions/1213999
https://support.mozilla.org/en-US/questions/1261244
https://www.reddit.com/r/Thunderbird/comments/rimjc4/thunderbird_change_timezone_in_received_date_of...
