I've got a POP server (dovecot, more than 200 clients) which I want to replace with Zimbra. This server has a DNS alias (CNAME) "pop.domain.com". What I want to do is :
- shut down mail arrival on the dovecot server,
- synchronize all the mailboxes with the empty Zimbra server,
- change "pop.domain.com" DNS alias to the Zimbra server.
This way, the Thunderbird clients wouldn't have to be reconfigured. Transparent POP migration.
*The* problem is that all the mails which have been kept on the POP server by the clients will be downloaded again by the clients (duplicated messages in Thunderbird). That's because Zimbra and dovecot don't answer the same IDs when replying to the POP "UIDL" command.
Is there a way, in Zimbra, to configure / set the message IDs ? Or to tell Zimbra to use the X-UIDL or X-UID mail header as IDs ?