If you are looking for the bset solution to backup your emails in PST format then you can use The Softaken IMAP Mail Backup Tool is a safe and simple solution to back up IMAP mailboxes to PST if you want to. It works for people who know a lot about computers and people who don't. This freeware lets you safely download and export all of your IMAP emails to PST format without losing any data. To back up your IMAP account, just enter the server information and login information, choose the mailbox folders you wish to back up, choose PST as the output format and start the process. It works with all the big email providers that use IMAP, like Gmail, Yahoo, Outlook.com, and others. The utility makes sure that the migration is 100% exact and keeps the folder structure and email integrity. This makes it the best way to easily back up IMAP mailboxes to PST. It is also provide a free demo trial  before puchasing.