Dovecot behind Load Balancer

Jean-Daniel Dupas jddupas at
Wed Jul 10 12:44:35 EEST 2019

> Le 10 juil. 2019 à 10:24, Paolo Daniele via dovecot <dovecot at> a écrit :
> Il 10/07/19 10:20, Aki Tuomi ha scritto:
>>> On 12/06/2019 20:02 Paolo Daniele via dovecot <dovecot at> wrote:
>>>  Hi,
>>>  i've a question for you.
>>>  I've two dovecot imap/pop server behind a zen load balancer.
>>>  Load balancing is made by lx4nat so the public ip address of my load balancer contact directly the dovecot servers.
>>>  Since few months i've a message from thunderbird that i've reached the imap limit login for ip.
>>>  I've triend to increase the max user ip parameter but sometimes i've the same problem.
>>>  It's a strange things that actually i'm able to mitigate by reduce the number of cached connections in Thunderbird but it's not normal.
>>>  What do you think about that?
>>>  Maybe there's some tuning that you can suggest.
>>>  Thank you,
>>>  Paolo
>> Have you ensured, by checking logs, that the connections are seen by dovecot to come from public IP addresses?
>> Also, thunderbird is known to open lots of concurrent connections.
>> Aki
> Yes,
> connections are coming from the ip address of load balancer (also checked with a netstat -an)

If connection are seen as coming from the IP address of the load balancer, isn't it normal that dovecot complains ? 
That means that dovecot sees all connections as coming from a single client, which would explain why you reach that limit.

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