Hello there exabyte. We have read your message. We try to help you.

ok the emails that pop up may seem to contain corruption. This could be what could be going on in your inbox. Delete all existing emails that you want to keep to a separate folder. delete all inbox topics you no longer want to keep. When the inbox is emptied and appears to be empty there is nothing left in it. rightclick on inbox and select Compact Empty and compact the Junk folder.

https://support.mozilla.org/en-US/kb/compacting-folders

Greetings Firefox volunteer.

Thanks but this does not solve the deleted-email-coming-back problem in Thunderbird. It should be noted that these emails do not show up in the Inbox when other email clients are used. Furthermore, there may be a broader synchronization problem in that some subfolders created on the email server using the email client provided by the email provider does not show up in Thunderbird.

WHo is your mail provider?

I delete emails from my inbox, and they reappear within 2 seconds.