Import preserving IMAP UIDs

[andybalholm]

Is there any way to import messages into Stalwart from another IMAP server and keep the IMAP UIDs of the messages (and the UIDVALIDITY of the mailboxes) the same? If the UIDs change, many mail clients will re-download all the messages—which wouldn't be a good thing, because most of my users are on cellular data connections and pay by the megabyte.

The only mail server I've seen that has this capability is Dovecot, but that's the one I'm considering moving away from, so that doesn't help…

[mdecimus]

That's not possible unfortunately, Stalwart needs to use its own distributed UID assignment algorithm in order to keep each UID unique across a cluster. By importing externally assigned UIDs there are risks of an email being assigned the same UID twice.

[andybalholm]

That makes be curious. How does the UID assignment algorithm work?

[mdecimus]

Actually I was wrong, I was confusing UIDs with changeId assignment which uses snowflake ids.. IMAP UID assignment is sequential and the write transaction makes sure that the assigned IDs are unique within acluster.

Implementing custom UIDs could be implemented but the priority at the moment is releasing the webadmin.