Wayne Mery said

It's a bit after the fact, but if you jumped from TB 78.14.0 to using TB 140.6 without going through intermediate updates then you may have something corrupted.

Not possible. See TB 140.0 system requirements https://www.thunderbird.net/en-US/thunderbird/140.0/system-requirements/

Corruption or incompatibilities has nothing to do with the current version's system requirements.

At various versions prior to the current version of Thunderbird, conversions are done which don't happen by simply installing the current version. Going from 78 immediately to 140 will have skipped three major versions. See https://support.mozilla.org/en-US/kb/upgrading-older-version-thunderbird

OK, I transferred the Inbox: I hadn't realised I had to put it in Local Folders and not where the new inbox is.

OK, I transferred the Inbox: I hadn't realised I had to put it in Local Folders and not where the new inbox is.

We haven't asked what kind of account you have. Apparently IMAP?

In any case, you can do whatever you want with the messages now. Move them to another folder, including an inbox. But if you have an IMAP account and zillions of messages, copying the messages to the server would take a long time and may be unreliable (I don't know; I have seen reports of errors). It's safer to put them into local folders first, then decide what to do with them.

You also could have transferred it directly in the newly created "pop.xxx.xx" account folder in Mail in the new profile. But I still don't know how many accounts you had set up in your old profile and whether they were IMAP and/or POP accounts. So I am cautious, all the more since my initial procedure was very different from the way you are going now which seems a mix of transfer of single mbox files and using the ImportExport add-on.

Going from 78 immediately to 140 will have skipped three major versions. See https://support.mozilla.org/en-US/kb/upgrading-older-version-thunderbird

There is a misunderstanding. Tim has TB 78.14.0 on his old Mac running macOS 10.9.5, so he could not update to an actual TB version since his OS is not compatible with newer TB versions. Thunderbird simply would have refused any updates to TB 91 or TB 102. Obviously Tim made en error by transferring the TB 78 profile on the new Mac and make it run in TB 140. Or do you mean he should have installed TB 78 on the new Mac, transfer the old profile on the new Mac and then update in several steps to the actual version?

The second method would be more reliable

Unfortunately it is not obvious to users what is most appropriate.

That said, having used the first method is not necessarily the cause of the performance issue.

You also could have transferred it directly in the newly created "pop.xxx.xx" account folder in Mail in the new profile. But I still don't know how many accounts you had set up in your old profile and whether they were IMAP and/or POP accounts. So I am cautious, all the more since my initial procedure was very different from the way you are going now which seems a mix of transfer of single mbox files and using the ImportExport add-on.

Mapenzi, just for my learning: Is there a reason why it's better to put an inbox from an old profile into a POP account in the new profile than to make it a regular folder in the local folders account?

In my old TB I had 2 accounts, both POP server type. The new TB seems to have automatically changed the Gmail account to an IMAP account. I've not yet tried to set up the other account, that's my next job. So far as I can see everything else is now working normally. Incidentally nothing told me not to do what I did i.e. download a new TB and copy my profile into it.

2nd account successfully added. All now seems to be working normally. Thank you to all of you who contributed to this, much appreciated. A donation will be forthcoming.

Great tenacity Tim!

> Incidentally nothing told me not to do what I did i.e. download a new TB and copy my profile into it.

Indeed. Unfortunately I don't know how we'd communicate that information. Let us know if you have any suggestions.

2nd account successfully added. All now seems to be working normally.

Congrats, you are very gifted!

Thank you to all of you who contributed to this, much appreciated.