Yes, attempting to upload 20g is a huge problem, as IMAP was never designed for that. Getting your messages from a POP account to an IMAP account requires careful uploading, preferably in small chunks. Creating a manual filter to copy from local folders to the IMAP account is a technique with a history of success, but I encourage spot checking messages after the upload to ensure messages are complete. I have no idea on why you cannot delete the POP account, but others here may have suggestions.

Thanks David for your reply. Any idea what the filter prompt should look like from one inbox to another one ? (I mean from the IMAP inbox to the local folder inbox). Thanks :-)

The filter need be nothing special. Manually run, selecting one foder to send the other to receive. My understanding is that the filter slows the process and that in itself reduces problems.

Still not sure about this filter command, as here, some files need to be transfer from one inbox to another inbox. There is no copy command as such. In the subjet line, I should indicate "to" and my email address so that all inbox emails can be moved to the new inbox right? the thing is that I have sub folder /directories and it might be a whole message during the transfer. I've tried to install betterbird, but the problem is the same. Copy/paste files from inbox to inbox takes ...days and not all the files are being copied...gets stuck after few hours...:-( I think I'd have to go for Outlook, although I don't like it so much. Do you know any interesting alternatives where files transfer will be easier ? Thanks a lot !!

It may help to see a screenshot of your account's profiles. From your post, it seems you have subdirectories in your POP inbox, which is very unusual. Seeing a screenprint or other layout to show folder structure would be useful.

Thanks David. I did uninstall, but yes, definitly I can do that. will re-install and take few prints screens. back to you in few days. Txs.

Hi again. See attached a small footage over my betterbird. I did a new IMAP installation that now appears as "christian@grau.com". Note that I manually created the folder/sub folders. https://we.tl/t-X9gE1Wxe2E

Then I used the betterbird import function from an entire thunderbird profile (copied on my desktop).

You can see the "local folder, blue icon" which is how my previous POP3 thunderbird profile looked.

the other 'netidentity/neuf/gmail/orange are secondary emails, they're emply and can remain

The challenge is now to transfer the messages from local folders/local folders/inbox into christian@grau.com/inbox and all sub folder, outbox, etc.. When I tried that last time with cut/paste, my laptop got stuck...maybe because there are 40.000 messages over 4gb in the inbox? Note also, that as soon as I switch on the internet, betterbird starts synchronysing with old emails that are still in my server (until 2017, then I created a pop account..big mistake..).

Not sure if that can be of any help to understand, but whatever you can do...it is much appreciated :-) Thanks, Chris

The link didn't seem to work, but I'll try to assist anyway. If betterbird is syncing's the account, you may as well wait until finished. OR, you can adjust the synchronization settings to not sync all messages. Once the sync process stops, you can attempt the upload, which will be problematic at best. IMAP was not designed for mass uploads, so you may experience timeouts or incomplete message transfer. One possibility is to copy small groups over a period of time, or you could create a manual filter to copy the messages. That's no guarantee either, but the filter does slow the process and improves the odds of a successful transfer.

Thans for your reponse. Well, I must confess it's a bit complicated to copy/paste the messages, it's like the PC gets stuck and the job will never get done. A pity as I got used to Thunderbird for 20 years almost...but it looks like as if it's time to change client. Any suggestion for a good one...appart from outlook ;-) Cheers

The issue isn't Betterbird or Thunderbird so much as it's pushing messages 'uphill' to IMAP. If there are to be subfolders, I encourage doing the base first before uploading to subdirectories. And the filter removes you from the copy/paste scenario. If you're wanting a new client, TheBat! works well.

Thanks for that. I don't exactly what you mean by filter. The function does not allow to copy messages from one folder to another. What should I type ? if xxxxx contains yyyyyy then move to zzzzz. What should xxxx and yyyyy be ?? I've tried outlook, but there is no import messages option :-(

The condition could be anything that is always true, such as 'subject does not contain weinersnitchel and the action could be COPY message to imapaccount>inbox

quick update: I think am getting copy/paste the messages, takes time... I realise I have many doublons in some directories which is probably because I earlier tried to copy and cancelled.. I there a command to use in the filter tools to manage doublons? Thanks Chris

For duplicates, this addon may suffice: https://addons.thunderbird.net/en-US/thunderbird/addon/removedupes/

Hi, Thanks for the addons, very usefull. I'm almost done setting my betterbird account. Took me a week or so. The main issue was that my host server only offers 10g, and I had 20g of messages. So I have to create local/folders as archive and for ex. store all messages that has a large attachement. Indeed a tedious tasks dealing with over 40.000 messages... Thanks for your help mate!!! Cheers