If you have changed your working email account and want to transfer all of your existing mail into the new Business or Enterprise email account, firstly, you will have to log in to your new mail service.
Locate the Settings menu on the top right corner. There, you will have to locate the Advanced Settings (Beta) section and in the Import mails window fill in the necessary information:
- The old/source email address.
- The old/source email account's password.
- IMAP Host/IP Address.
- IMAP Port.
Since your old mailboxes created in hPanel will no longer work, you will be able to transfer your old email account's mail to the new account with the old mailbox's details, which you can locate by visiting your old email account via the Check your old mailboxes button in the pop-up banner of the new mail section :)