A way to set/change POP mail IDs ? (UIDL command)

[osmedts]

Hello,

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 ?

[dkarp]

No. But you can tell the Zimbra POP server to hide all messages received before a certain date. That's controlled with the "zimbraPrefPop3DownloadSince" server attribute.

[osmedts]

Thanks for replying, but I can't use that since I don't have such control over the clients (if and when they download new mails).

The transparent one-time POP migration seems compromised. I'm investigating a "one user at a time" migration, per user request.

[mmorse]

Dan's talking about the server side setting:
In 5.0.6: Bug 27293 - Provide a way (presumably a config/setting) to limit POP downloads
In 5.0.7 user UI controls: Bug 27912 - Provide web client config/setting to limit POP downloads

As an admin you could configure that time better:
zmprov -l ma user@domain.com zimbraPrefPop3DownloadSince 200807151000000Z

[mmorse]

So the new process would be:
- shut down mail arrival on the dovecot server
- synchronize all the mailboxes with the empty Zimbra server (impasync?)
- set the zimbraPrefPop3DownloadSince on all accounts
- change "pop.domain.com" DNS alias to the Zimbra server (might adjust your TTL down just a little in advance)

[osmedts]

The problem with this solution is that the POP clients won't have the mails received from their last check to the migration time (because they will switch to the new server - Zimbra - which won't let them download those mails through POP because of the zimbraPrefPop3DownloadSince setting). Some people are not in the office since few days or weeks. I don't see how to avoid duplicates *and* client's reconfiguration.

[mmorse]

Ya there's a 'barrel full of monkeys' when it comes to caveats - POP is just oh so fun!

So sounds like you're planning a Split Domain - Zimbra :: Wiki one at a time for migration, then having them update server addresses manually. Which kinda defeats the 'transparent' migration intent, but might just be the way to go so you're not in a frenzy.

Crazy idea:
Don't know your environment (& if you can get a day with all 200 capable!) but you could do what I like to call 'an informed day in advance' where you go "Hey this Friday everyone needs to sync their mail between 4pm-5pm" queue incoming/internal mail from 4pm on. Anyone who can't make it work with in advance to go "When's the last time you can sync?" (then disable they're login after their last sync so they can't mess it up -lol)

[osmedts]

That will be easy, no need for a split domain configuration : I already have MXs and mail router in front of the Zimbra server. So I'll just have to modify the mail transport address of each LDAP account to redirect to Zimbra. There's no zimbra-mta package on the Zimbra server, it will use our existing smtp server.

No need to disable old POP accounts too, I will give "information in advance" to add an IMAP account for Zimbra in Thunderbird I only needed POP for transparent migration, but if the users must modify their Thunderbird settings... it's better to use IMAP now. Then we'll introduce the full-featured WebClient

Maybe I should post an RFE to make the POP server use X-UID mail headers or something like that to reply UIDL commands ?

Thanks for helping,
Olivier

[osmedts]

Maybe I should post an RFE to make the POP server use X-UID mail headers or something like that to reply UIDL commands ?

Like dovecot uidl configuration : see "POP3 Migration" on Migration - Dovecot Wiki. That would have been perfect for a transparent migration

Or by allowing modification of IMAP mail UIDs. That way, imapsync could sync UIDs between IMAP servers, with a patch like http://www.linux-france.org/prj/imap...c.syncuid.diff. Hopefully, IMAP and POP UIDs will be the same