Switching properly keeps everything.
WHY SWITCH
POP3 downloads mail to one device and usually removes it from the server. Other devices never see it, sent items exist only on the device that sent them, and a failed laptop loses everything.
THE SAFE METHOD
- Do not delete the POP3 account yet.
- Add a second account in the same client, configured as IMAP with the same mailbox.
- Wait for the IMAP folders to appear.
- Drag or copy mail from the POP3 account's local folders into the IMAP folders. It uploads to the server as it copies.
- Copy Sent, and any folders you created.
- Verify in webmail that everything arrived.
- Only then remove the POP3 account.
WATCH THE QUOTA
Uploading years of mail to the server consumes disk space. Check the mailbox quota first, and archive genuinely old mail to a local folder rather than uploading all of it.
DOING IT IN THUNDERBIRD
Easiest here, because both accounts and local folders sit in one window and dragging works reliably.
