Master-Master replication question

[Rick Romero]

  Quoting Remko Lodder <remko at freebsd.org>:

>> On 11 Jul 2016, at 17:36, Rick Romero <rick at havokmon.com> wrote:
>>
>> Quoting "William L. Thomson Jr." <wlt-ml at o-sinc.com>:
>>
>>> You are not alone!
>>>
>>> On Wednesday, July 06, 2016 01:15:34 PM Remko Lodder wrote:
>>>> Dear list,
>>>>
>>>> I have setup a master-master replication setup. My primairy MX's send
>>>> email
>>>> over on a DNS loadbalanced way, so DNS is doing some kind of
>>>> round-robin
>>>> way of sending mail to both master servers.
>>>>
>>>> I found out, that on one of the two machines, the email
synchronisation
>>>> is
>>>> heavily delayed. Lets assume server A receives a mail from the MX; it
>>>> synchronises almost instantly with the other server.
>>>>
>>>> Whenever server B receives the email, it could take up to several
hours
>>>> to
>>>> synchronise the email, it seems that it is not detected prior.
>>>
>>> I have been dealing with this for months.
>>> http://www.dovecot.org/list/dovecot/2016-March/103680.html
>>>
>>> For a band aid I use  this crontab entry. On the 2nd mail server.
>>>
>>> */15 * * * *   root    /usr/bin/doveadm sync -u "*" remote:mail1
>>> <snip>
>>
>> Are you guys using LMTP to deliver from your MX server to the mailbox
>> server?
>
> Local delivery on the destination server is LMTP but the transport
between
> MX and destination server is just plain SMTP.
>
> I could try and revert to dovecot-lda and see what that does?
>  

  I don't think that'll help.  From what I understand, LMTP is required for
replication on delivery.

  Out of curiousity, why do you use SMTP from the MX to the destination
server instead of LMTP?