Convert a POP account to a IMAP account

This article was written for Thunderbird but also applies to Mozilla Suite / SeaMonkey (though some menu sequences may differ).

Thunderbird doesn't support converting a POP account to a IMAP account. It's not as simple as editing the accounts server settings. Its possible to convert the account by modifying some settings using the config editor and moving some files but that requires understanding how accounts are implemented that most users don't have. Its much quicker and safer to create a new account and move the messages to it, and then delete the old account.

• Backup your profile using something like Mozbackup.
• Stop the POP account from checking for new messages by unchecking the two boxes for checking for new messages in Tools -> Account Settings -> account_name -> Server Settings
• Create the IMAP account using Tools -> Account Settings -> Account Actions -> Add Account
• Move the messages from the POP account to the IMAP account (or to Local Folders). If a folder with the same name doesn't already exist in the IMAP account you can just drag and drop it to the IMAP account. Otherwise select all of the messages you want to move (Control-A or Edit -> Select -> All) and then use Message -> Move to move the messages to the remote folder.
• Compact the folders in the POP account using File -> Compact Folders.
• If you have any message filters you can reuse them by moving the "msgFilterRules.dat" file from the "local directory" of the POP account (or Local Folders if you had configured the POP account to used a global inbox) to the "local directory" of the IMAP account. The "local directory" is specified at the bottom of the server settings pane, next to the Browse button.

  If this is too confusing just create new message filters.

• Verify the IMAP account is working okay and you didn't forget to move any messages. Then delete the POP account using Tools -> Account Settings -> Account Actions -> RemoveAccount.
• If you had created multiple identities for the POP account you will need to re-create them for the IMAP account. This is a optional feature mainly used to let you use a different From: address and/or Sent folder when composing a message.
• Thunderbird doesn't delete the files used in a deleted account. You may want to exit Thunderbird and delete the subdirectory named after the POP server. However, since you emptied and compacted its folders its not wasting a lot of space.

See also

• IMAP advanced account configuration
• Importing folders
• Profile backup
• Recovering deleted mail accounts