I just had some thought about best practices for moving messages between accounts using the Mac Mail App.
The Reason to Move Mail
One reason is that might want to migrate messages from an Office365 or Gmail to an iCloud Account. Outlook on Windows allows you to Import and Export PST Files at will which makes mailbox migration a cinch. However on Windows importing a PST file with a large numbers of emails can cause iCloud to throttle or ban you especially if you have a large PST. But since we are using a Mac and iCloud lets see if we can get this done without Windows.
Things to Keep in Mind
Mac Mail is slow and queues up move jobs in the background. You can see these jobs once they are in progress by going to Mail -> Window Activity and checking win the lower right hand corner. Also the Mac Mail App is file based so the emails are stored in files in ~/Users/Library/Mail/V6.
Some Methods to Try
- Shrink the mailbox you are copying from first. Use an App like clean.email or Mailstrom to shrink your mailbox to manageable size so your are not copying Multiple Gigabytes of emails.
- If you are using Office365 or Exchange, configure Mail to use IMAP for retrieving emails instead. You will need to set ups the account as “Other and enter your IMAP credentials.
- Have Patience. Wait for Mail to Queue up the Job and perform it. You may also be waiting on the iMap Server.
- Create local “On My Mac” Mailbox as a holding area for the emails you are moving to the new account. The “On My Mac” folder is like a staging area.That way only 1 imap Server is in play at a time. Move your emails from the original account to the On My Mac folder. Once that copy completes move the emails to the new account.
- I find that dragging and dropping from Mailbox to the other works best
- Only drag and drop several hundred emails at one time not thousands.
- Closing Mac Mail Aborts the process and allows you start over. Closing can be helpful if the moving process gets stuck.
- If the drag and drop does not work the first time try it again.
- Also try splitting your mail up into sub-folders since a folder you made might accept a copy sooner than a system folder like Inbox or Sent.
- Also try Exporting the Mail as an MBOX file and reopening it and mounting it the Mail Folder tree. From there you can copy out the emails.
- Try AirMail and use Mailbox rules to move the messages.
I hope this helps and that the next version of Mail has better migration tools in place.