I had a similar problem when around last month I decided to ditch Thunderbird. Now perhaps (hopefully) drag'n'drop or copy-pasting will work for you (and if it does, there is nothing wrong with it), but for me and my thousands of mails, these procedures didn't get me far: usually, after 15-500 mails, Thunderbird simply dropped the connection. After ruling out the option of copying each message independently (and then checking if it really got copied), I looked around in the internet and found
this Python script simply named "IMAP Upload".
Please note that I am neither gaining profits from suggesting this nor am I the developer of this tool.
Although it seems that the tool isn't maintained any longer, it still worked well (after fiddling around quite a lot - see below).
My workflow:
- Saving everything from the IMAP-account locally (and temporarily shifting it in separate (sub)folders) - This is just a precaution: That way, in the case of failure, your nicely sorted inbox won't get messed up.
- Just using Thunderbird's Profile-structure for exporting the POP-account failed miserably, so I ended up using ImportExportTools to export every (sub)folder separately (maybe a bit paranoid; but for me, exporting them all together didn't work)
- Then, I'd run
python imap_upload.py --gmail --box=<ENTER_FOLDER_NAME> [email protected] --password=password --retry=10 <THUNDERBIRD_PROFILE_FOLDER>/Profiles/<YOUR_PROFILE>/Mail/<POP-ACCOUNT>/<FOLDER_EXPORT_NAME>.sbd
(of course, you have to fill in everything inside < >
and your username and password. ;-) )
- It's best to check if the
--box
-value was accepted after each upload (For me, 2/35 were not properly created and the mails ended up in the main inbox, though I cannot rule out typos or mistakes on my side).
As to your question regarding lost information: the dates were not altered and I still have every attachment, every Umlaut and every Smiley in my mails. That is to say: My randomly handpicked comparisons (and some tools) say so.