Horcrux

Horcrux lets you automatically backup your mails from any IMAP supported email accounts with great ease. The best part is, you have an option to restore the backup'ed emails to any other email account, retaining all your tags/folder hierarchy.

"Horcrux is handy since you don't actually have to think about it when it's running." - Lifehacker

Note: The first backup usually takes a lot of time. So, please do wait if you have a large email account.

Features:

• Tested with iCloud, Gmail, Google Apps, Microsoft Exchange. List of Supported Servers http://thehorcrux.com/list.html
• Supports multiple email accounts
• Add the accounts, set the backup frequency and it'll unobtrusively backup emails in the background
• Emails can be archived as a ZIP file making your data portable
• Clever restore process that'll skip already existing emails
• Stores emails in open format (.eml) which can be opened in clients like Apple Mail

Please feel free to contact us in case of any problems https://thehorcrux.com/support

Note: Google and Microsoft are trademarks of their respective owners.