Migrating mailboxes between mail servers

NOTE: the process requires around 15 minutes configuration of imapcopy and, in some cases, stunnel) on the 3rd server. Provided links are enough to quickly set up the migration, so I will not be copying the content of other websites here.

1. Install IMAPcopy utility on any inbtermediary server. DONT USE SOURCE OR TARGET SERVER

2. In specific cases you might need to establish Stunnel for SSL communication - follow this instructions