Massive alias / bulk delivery problem

Aki Tuomi
Tue, 14 Jul 2020 08:08:43 -0000

On 14/07/2020 10:52 gnd <<a
href="mailto:gnd@itchybit.org">gnd@itchybit.org>
wrote:








    Hello list,





    we are experimenting with using Dovecot as part of a simplified mail


    stack with SQL for a internal messaging / notification system for our


    customers. Sometimes we need to send a message to thousands of customers


    at once and we do it by having aliases resolve to 10k and 20k+ mail


    accounts.





    When we send such a message the server load (obviously) is very high for


    a few minutes (in case of an alias containing 10k addresses its around


    6-7 minutes for a 2 core machine with load around 20-30).





    Are there any optimizations or ways how to design the system around this


    problem ? Eg. is there a way how to deliver messages more slowly, and


    spread the load over longer time ?





    The stack is very simple with Postfix receiving the messages and Dovecot


    acting as a LMTP and IMAP server. Mailboxes are in the Maildir format on


    disk. Customers get the messages on login, a PHP script connects to the


    mail account associated with their ID via IMAP and sends unseen messages


    in the form of a JSON.





    Best regards,





    gnd/






   Can you provide output of doveconf -n?





   Also, verbose_proctitle=yes gives more insight what the processes are doing.





   Aki