Hypothetical scenario:

  1. The IMAP inbox has two messages, A and B.
  2. Thunderbird syncs, and downloads both A and B.
  3. A new message C, is delivered to the IMAP server.
  4. B is deleted from the server by a different client.
  5. Thunderbird syncs again, downloads C and deletes the local copy of B.

What I want is to prevent the local deletion of B. I want it to stay locally until explicitly deleted from within Thunderbird. I understand it won't be on the server any longer, I just want to keep it locally.

Any thoughts?

2 Answers 2


I don't know if it's possible within the IMAP folders, but you could create a Message Filter in Thunderbird that copied new messages from the IMAP folder to a folder in Local Folders:

First, create a folder in Local Folders to keep the messages in

From the IMAP inbox,
go to Tools / Message Filters
click New
give the filter a name
click Match All Messages
in Perform these actions select Copy Message To and then select the folder you created in Local Folders
click Ok

It should run automatically for all new messages, and you can run it manually by clicking Run Now in the Message Filters box, or from Tools / Run Filters on Folder

  • Exactly what I do with TB. All incoming mail is put to a local folder (specific folders on other rules, common folder for the rest).
    – karatedog
    Dec 20, 2011 at 10:11
  • 1
    It didn't when I just tested it... I sent email from an IMAP account in Thunderbird; it went to the sent folder in IMAP, but wasn't copied to my local folders. When I replied to it, the incoming reply was copied. About the same time I received an email that was filtered by the server into a different folder, and that didn't get copied by the rule. It sure looks like it's only picking up messages delivered to the Inbox - though if that isn't the behavior you want, I can't see a way to change it. (Thunderbird 8.0 on Windows) Dec 20, 2011 at 15:01
  • Worked like a charm still. Thank you! :D Aug 5, 2021 at 2:32

Solution below works after your imap account has been setup.

Go to into your profile folder of your old pop account and copy your inbox and inbox.msf into your local folder directory. eg.

C:\Users\Name of your account\AppData\Roaming\Thunderbird\Profiles\i0mi3phf.default\Mail\

Rename them to the Trash and Trash.msf. That will allow you to see your emails inside thunderbird without it being deleted by your imap account update. Open up thunderbird and drag and drop your emails from your local trash into your inbox of your new imap account. It will then sync your original emails to your new imap email server. :)

I tested this solution on my laptop and confirmed the uploaded emails using my cellphone.

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