Something not far from "pop" the e-mail for local storage, in that it's removed from the server. This is with IMAP, of course.
The only thing that actually makes POP destructive is the clients' use of the DELE
command to delete each message that was just retrieved. So you can do it via IMAP using exactly the same operations as in POP:
- Get a list of messages.
- Retrieve a message.
- Delete the message.
- GOTO 1
If this is a one-time job, probably any desktop IMAP client (such as Thunderbird) will allow you to a) drag and drop all messages into a local folder or into another server, or just b) select all messages and delete them.
For periodic one-way sync, fetchmail
supports the same "fetch and delete" process with IMAP as it does with POP. Getmail probably does as well.