This function is only available for the Advanced plan.
Back up your emails on PC
You can use the email backup function to free up space or create copies of important emails on your PC.
You can back up your emails by clicking 
that appears when you hover the mouse over a mailbox and then 'Backup', or making changes in Settings as below.
PC Web
- Click
on the top. - Click
on the top right in Mail. - Click 'Settings'.
- Click 'Manage/filter mail > Manage/backup Mailbox'.
- Click the 'Backup' on the 'Manage' column of the mailbox you want to back up.
- By clicking 'Download' on the right, save the .zip file to your PC.
The .zip file contains the data of each email in the .eml format.
If the mailbox to back up is 2GB and larger, files are created in units of 2GB. If a mailbox contains more than 65,000 emails, files are created in units of 65,000 emails.