It appears pretty easy to migrate an existing GMail account to another IMAP server, i.e. not GMail/Google server. There is an excellent synchronization tool – imapsync, which checks and downloads all the mails of an user account from one IMAP server to another IMAP server per user. The tool supports Google’s GMail accounts and their specific naming including the labels folders peculiarity (some folders in GMail may not have any physical emails, but just to show emails from another folders with specific labels). It’s worth mentioning that the imapsync works only only with GMail accounts, but it can be used to migrate from one IMAP server to another IMAP. The key here is the source and the destination server should support IMAP protocol.
Imapsync is an IMAP transfer tool. The purpose of imapsync is to migrate IMAP accounts or to backup IMAP accounts.
GMail will expose the labels as folders and in some early versions of the imapsync tool the emails with multiple labels may be shown in multiple folders and be duplicated. The version used here did not duplicate any email, even some emails were shown in multiple GMail folders.
There are two GMail settings to enable before proceeding with the migration:
- Enable “Less secure app access” or if 2-Step-Verification is enabled use App Passwords
- Enable IMAP, which is disabled by default.