On 14/07/2020 10:52 gnd <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/