An IMAP account perhaps?

Hello - thanks for your reply. Yes my email accounts are all IMAP, but the emails that are getting deleted automatically, are only from one account, ie the same account every time. The account settings are the same for all the accounts, so why is only the one account effected?

Anyway thanks for taking the time to respond.

Regards Tony Brown

As you would be aware IMAP is synchronized to the server, I suggest you contact your mail provider. My guess is they are aging your mails and applying their own deletions settings at the server level, which then synchronize to other devices including Thunderbird.

Ok thanks for your information. I think this maybe the answer that will help.

Thanks again for youe time.

Regards Tony Brown