I suspect you are accustomed to using POP and have for some reason set it up to use IMAP.

Upgrading the version of Thunderbird does not (can not!) change from one account type to another. And I have seen no change in the retention settings.

So, what else has happened?

Yes, the laptop is set up as IMAP and the tower as POP. As you say, I have never had this kind of issue before. When I set up the laptop TB I took the "General" not custom install and I guess it picked the IMAP for me. I do not see a way to change it in the account settings. I am not very experienced in the email settings etc. Do I need to do a new TB install with the different POP setting on my laptop?

Thanks for the quick response.

You can't change an existing account from POP to IMAP or vice versa. Just add it again.

When you add an account there is a point where Thunderbird shows you the settings it has found. It will almost always offer IMAP. In some cases it recognizes that both POP and IMAP are available and lets you choose between them.

If you want POP and have reason to believe that it is supported but is not offered in Thunderbird, then you need to override the settings manually and insert the appropriate settings. You should be able to find these on the email provider's website.

But if you have installed Thunderbird on a new machine, you could avoid all this by copying the profile from an older machine.

https://support.mozilla.org/en-US/kb/profiles-tb

Personally, I'd use IMAP on all of my machines, and on the "master" computer, I'd select those messages I wanted to keep but also remove from the server, and move them into the Local Folders account. Doing this would, in due course, automatically remove these message from the other machines, so you only have to delete once.

Got it. Thanks. I know where to go from here and I now know more about the set up of the email program.

Thanks again, big help.

One final comment. I copied the profile as you suggested to the machine I wanted to change. Worked perfect, big thanks.