Dovecot behind Load Balancer

Paolo Daniele paolo.daniele at
Wed Jul 10 11:31:47 EEST 2019

Il 10/07/19 10:27, Aki Tuomi ha scritto:
>> On 10/07/2019 11:24 Paolo Daniele via dovecot <dovecot at> wrote:
>> 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)
>> I know that thunderbird has this problem and i haven't problem since the
>> numbers of email domain increase.
>> I'm not sure the impact of rising the max user ip to an higher value in
>> terms of ram consumption and cpu
>> Any suggestion?
>> Thanks for your answer!
>> Paolo
> What's your current limit? The default value is 100.
> Aki

mail_max_userip_connections = 500


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