I recently had to modify the IMAP server for about 5 mail accounts in Thunderbird and after doing so, for each account I only see new messages that arrived to the new mail server.

To make it more clear, I had 5 accounts like this: info@mydomain.com, support@mydomain.com, ..., configured with oldmailserver.com on port 993 and for all of them I changed the incoming mail server to newmailserver.com (yet on port 993).

After doing so, I no longer see all messages that I had received with oldmailserver.com.

Now, I am sure that Thunderbird did not delete the messages physically because my c:\users\username\AppData\Roaming\Thunderbird\Profiles\rd4y3dca.default folder is still 15Gb big. Specifically, in the ImapMail folder inside of it, I have many subfolders named like this: mail.mydomain.com, mail.mydomain-1.com, mail.mydomain-2.com, mail.mydomain-3.com with the highest numbered one being the only to have a last modified date of today (and the second most recent one having a last modified date of about 6 months ago). Inside that most recent folder, I have one 1.5Gb INBOX file and an INBOX.sbd folder, containing other quite big files named "sent", "draft", "trash" (all the typical email account folders).

How can I proceed to restore for each account the old messages, so that they display together with the messaged received with the new server?

I am not sure what all those folders are and how I can proceed to keep the new server configuratio

  • 1
    Remember that IMAP is essentially folder syncing with the server version being the master. What you are seeing is what I would consider expected behavior. If you can still connect to the old server you can copy the emails to the new inbox. As far as TB knows they are not the same inbox. – Tyson Apr 24 '16 at 18:46
  • In my case old server was shut down and not available anymore. I managed to solve it though, see my answer. – jj_ Apr 24 '16 at 22:51
  • @Tyson I know this is the expected behavior. But there is no expected behavior in how the old mail messages should be managed for when the server is changed (getting rid of them? Informing the user that they will be kept in a file? Maybe even merging those already on disk with new ones in case the account name will be exactly the same?) so perhaps a complex mail client such as TB could also handle this situation and guide the user (as it does for many other aspects) rather than just letting them alone wondering what to do. – jj_ Apr 25 '16 at 17:08
  • It's true that any software could be better. Generally this seems to most often be dealt with via migration/import tools at the server level (not client), importing directly from old to new bypassing the client altogether. In the case of any server migration, email or otherwise, the admin or developer has to address what's relevant to migrate and what is irrelevant trash. If you had many users migrating this would be a must especially if they were all sharing an office LAN. Sorry you didn't see the big picture in advance, but glad you were able to recover so easily. – Tyson Apr 25 '16 at 17:20
  • That I did not see the big picture is just you giving judgment without knowing things. I could not operate at server level because of constraints (the server admin decided that the mail server would have been shutted down in a matter of hours, the server was not physically available to me and the mail amounted to more than 15Gb (not feasible to be sent at available connection speed here)). We already knew that all email had been also downloaded from the clients, so we went on with that approach. The thing that went wrong is TB not telling anything at all about what it would do with old mail. – jj_ Apr 25 '16 at 17:36

I managed to restore the messages following this post:


Luckily Thunderbird was configured to save local copies of inbox messages and sent messages (that's why I still had big files under ImapMail account subfolders). I don't know if this is the default setting for Thunderbird (it was not me to install TB in the first place), but this saved me.

Interesting thing is that the big files, for example INBOX, is not deleted and recreated when modifying the server, but it looks like new messages are appended to it even though the old ones are not readed anymore, so what I did was copying them to c:\users\username\appaata\roaming\thunderbird\profiles\<profilename>\mail\local folders and now I got everything back.

Once copied it is safe to delete them from their account subfolder, so that the mail files for each account (inbox, sent, ...) will be recreated from scratch and contain new messages only.

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