Imapsync is a widely used tool for migrating emails between IMAP servers, praised for its effectiveness in handling large mailboxes. Several users have shared their positive experiences, emphasizing its reliability over the years. Originally, users had access to the source code for free, but it now appears that the binaries are behind a paywall. There are questions around its compatibility with Google Workspace migrations, with alternative tools like mbsync/isync also mentioned for users interested in different functionalities such as local downloads. The general sentiment in the comments is highly favorable, considering it a must-have for email migrations, although users are exploring other options for flexibility and local management.