DO not overwrite anything. It is not necessary and can even be dangerous. You could lose all your stored messages.

All you want to do is to take POP mail that is now stored on your local machine, and make it available and readable to all users who access your mail account on your IMAP server.

It involves moving the POP mail that is stored on your computer and uploading it to your IMAP account over the internet.

Thunderbird can do that.

The following article has info on the procedure.

http://www.howtogeek.com/198559/how-to-import-your-pop3-emails-into-an-imap-account/

If you have a personal (non-business) internet account, your internet upload speed is often one-tenth as fast as your download speed. (Varies by provider). Uploading hundreds of emails may take a considerable amount of time. Allow for this.

TB38.2 Win10-PC

Thank you for your reply. I was aware of what you outline.

I have a different problem.

POP inbox has 100 emails. IMAP inbox has 10,000 emails, which had been archived on the server. I no longer need most of them.

It's not that the 100 are all after a certain date, so I can't just delete the ones before such a date.

My question was more: is the file structure for mail in inbox and related inbox.msf the same for both POP and IMAP? If so, then I could simply, in Windows Explorer, copy the POP inbox file from the POP folder and drop that into the IMAP folder.

LadislausRabinseifner said

Used POP for years3, Windows 7, GMAIL. Converted to IMAP following excellent instructions. On GMAIL server, inbox still has a few 10K messages that I long since deleted on my local computer. The POP inbox reflects the state I'd like to use. Can I copy the POP inbox into the IMAP account, overwriting the IMAP account's inbox? I know where to find the profile.

After re-reading your original question, I wonder if my answer actually addressed your concern.

Now I think that what you want to do is change the IMAP inbox to show only those messages that you have saved on your local machine and delete all others. Is this the case?

If so, this can be done in TB.

Basically, TB gives you a view of your IMAP account with the ability to sync changes. If something is added in IMAP, it shows up in TB. If something changes in TB, the changes can be synced to IMAP.

In TB, open your IMAP inbox and select all the messages inside, then 'MOVE to..." (not 'COPY to...') all the messages to a new folder located in 'Local Folders'. (This is important. Transfer to a folder that is NOT in IMAP). Be patient it may take time. Check that your IMAP inbox is actually empty. If there is a lot of messages the server may have restrictions on bandwidth. When finished your IMAP inbox should be empty and you have your old inbox messages copied to your local machine.

If you then open your POP inbox, select all the messages and 'COPY to...' the IMAP inbox, you will repopulate the IMAP inbox with your selected messages. Have more patience, uploads typically take longer than downloads.

You should verify that all messages have been transferred properly, attachments work, etc. Fine tune your inbox to make sure that all of your important messages are copied.

Only then can you delete the Local Folder copy of the old IMAP inbox, and the contents of your POP inbox.

You can even move folders and the folder structure to/from the IMAP server.

http://www.howtogeek.com/198559/how-to-import-your-pop3-emails-into-an-imap-account/

sent before i saw OP's 2:22 posting

LadislausRabinseifner said

Thank you for your reply. I was aware of what you outline. I have a different problem. POP inbox has 100 emails. IMAP inbox has 10,000 emails, which had been archived on the server. I no longer need most of them. It's not that the 100 are all after a certain date, so I can't just delete the ones before such a date. My question was more: is the file structure for mail in inbox and related inbox.msf the same for both POP and IMAP? If so, then I could simply, in Windows Explorer, copy the POP inbox file from the POP folder and drop that into the IMAP folder.

Then simply move emails from IMAP inbox to a temp folder on IMAP, effectively emptying it. Then copy messages in POP inbox, paste into IMAP inbox. When happy with results, send temp folder on IMAP to trash, delete contents of POP inbox.

Thank you for your responses. Sounds reasonable. Will try today.