Having just 1 domain and ~50 emails (and more to come) I get a lot of errors from users in using email with roundcube or thunderbird.
In a few words problems are: "imap folder is not accessible", "can not save message in sent folder", "error on connecting to mail server and always requesting the password", and others.
I've tried to increase the number of limits and instances to smtp and imap.
I did some tweaks in dovecot to performance.
But none of that solved me.
Some observations done on working processes and found that very often "sendlimiter" consumes >99% of CPU. (I have 3 CPU on that server and 16GB of RAM).
Does anyone know how to fix that?
As a temporary solution, but not the fix, i need to restart the server every half a hour, but again - this is not a solution for a system with 100-150 emails that will come.