How to Move Email Between Two Mailboxes With IMAP (Drag and Drop)

Moving mail from one mailbox to another sounds like it needs a migration tool. For anything up to a few gigabytes it does not: add both accounts to one desktop mail app over IMAP and drag folders across. The messages travel through your computer to the other server with dates, flags and attachments intact. Here is how to do it cleanly.

Quick summary

• The IMAP details for both mailboxes. For an OquMail mailbox: server mail.oqumail.com, port 993, SSL/TLS, username is the full address. For the other side, whatever that provider publishes.
• A desktop mail app. Thunderbird is free, cross-platform and handles large drags well; Apple Mail and Outlook also work.
• Enough free space on the destination mailbox. Check the source size in webmail first.
• A stable connection and time. Budget roughly an hour per gigabyte on a typical home connection; leave it running rather than watching it.
• Add the source account: Account Settings, Account Actions, Add Mail Account, enter the address and password, then Configure manually if it does not detect settings. Repeat for the destination.

What you need

• The IMAP details for both mailboxes. For an OquMail mailbox: server mail.oqumail.com, port 993, SSL/TLS, username is the full address. For the other side, whatever that provider publishes.
• A desktop mail app. Thunderbird is free, cross-platform and handles large drags well; Apple Mail and Outlook also work.
• Enough free space on the destination mailbox. Check the source size in webmail first.
• A stable connection and time. Budget roughly an hour per gigabyte on a typical home connection; leave it running rather than watching it.

Step by step in Thunderbird

1. Add the source account: Account Settings, Account Actions, Add Mail Account, enter the address and password, then Configure manually if it does not detect settings. Repeat for the destination.
2. Right-click each account, Subscribe, and tick every folder you want to see. Thunderbird sometimes hides folders until subscribed.
3. Select the source Inbox and wait for the message list to fill completely; the status bar at the bottom reports progress.
4. Create matching folders in the destination account (right-click the account, New Folder). Keep names identical to avoid confusion later.
5. Open the source folder, click one message, press Ctrl+A (Cmd+A on Mac) to select all, then drag onto the destination folder. To copy rather than move, hold Ctrl (Option on Mac) while dragging.
6. Move Sent, Drafts and any custom folders the same way. Do Inbox last, because new mail keeps arriving there.
7. Compare message counts per folder in both webmail interfaces. Numbers should match.

Apple Mail and Outlook notes

• Apple Mail: add both accounts under Mail, Settings, Accounts. Drag folders in the sidebar; holding Option copies. Mail shows a progress bar under Window, Activity.
• Outlook: File, Add Account for each. Drag folders between the accounts in the folder pane. Outlook may pause on very large folders; move in batches of around 2,000 messages if you see "operation failed".
• On all apps, do not put the computer to sleep during a move. A sleeping laptop leaves a half-moved folder.

Copy first, then delete

Drag with the copy modifier (Ctrl or Option) so the source folder stays intact. Verify the counts, open a handful of messages with attachments in the destination, and only then delete from the source. A move that is interrupted halfway is easy to resume when the originals are still there and impossible to fix when they are not.

Pitfalls

• POP instead of IMAP on the source. POP has no folders and may re-download everything; use IMAP on both sides.
• Gmail as the source: "All Mail" contains every message, so dragging from All Mail and from Inbox duplicates them. Drag from Inbox and from labels you actually use.
• Provider throttling. Some providers limit IMAP bandwidth per day; if the move slows to a crawl, let it run overnight.
• Folder name characters. Slashes and dots in folder names can be interpreted as sub-folder separators on some servers; rename such folders before moving.
• Duplicate messages from a restarted move. Thunderbird's Remove Duplicate Messages add-on cleans these up.

Common questions

Can I move mail between two accounts on the same host?

Yes, exactly the same way. Between two OquMail mailboxes the move is fast because both ends are on the same server, but it still passes through your computer, so keep the app open until it finishes.

Will the messages look forwarded or lose their dates?

No. IMAP moves keep the original headers, so the sender, date and reply history are unchanged. Only the storage location differs.

Is there a way to do this without a computer?

Some hosts offer a server-side import that pulls mail from another IMAP server when you enter its details. If yours has it, it is faster and does not depend on your connection. Otherwise a desktop app is the universal method.