Migration and backup
Plan a mailbox move before changing DNS or closing the old service.
Before you migrate
Create and test the destination mailbox, confirm available storage, and keep the old mailbox active. Record important folders and estimate the amount of mail that must be transferred.
Copy messages
Use the mailbox import option in Webmail settings or a trusted mail client that can copy between accounts. Source credentials are used only for the transfer flow and should be changed afterward if exposure is suspected.
Verify the result
Compare important folders and recent messages, send and receive test mail, and check timestamps and attachments. Keep the old service available until the result is verified.
Keep independent copies
Export or otherwise preserve messages that are legally, financially, or operationally important. Do not rely on any hosted mailbox as the only copy of irreplaceable data.