Replication: does it work in both directions?

David Carter dpc22 at
Tue Nov 13 05:04:16 EST 2007

On Sun, 11 Nov 2007, Rich Wales wrote:

> So, I would have replication set up going both directions between my two 
> servers, but the sets of users handled in each direction would be 
> disjoint.  Each user would be assigned to one IMAP server (the master 
> for their mailbox collection), and the other server would be their 
> replica and act as their backup.

We do this. It is quite useful to be able to bounce users back and forth 
between the two machines in a pair so that servers can be maintained 
(patches, O/S upgrades, whatever) without any user visible downtime.

Three caveats:

1) It won't work with shared mailboxes.

2) I'm not running the same replication code as the rest of you (though
    replication in 2.3 is based on an old version of my code). I seem to
    remember Ken raising an objection when this last discussed a year or
    two back now. The objection may just have just been (1).

3) Sanity checks are good:

    USER dpc22
    NO IMAP_INVALID_USER Attempt to update master for dpc22

David Carter                             Email: David.Carter at
University Computing Service,            Phone: (01223) 334502
New Museums Site, Pembroke Street,       Fax:   (01223) 334679
Cambridge UK. CB2 3QH.

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