>Yes MTA is a problem. When I stop sending emails and let Cyrus IMAP finish >the mails queued in Sendmail, I got more that 20 messages per second. >I have tried to use Postfix. Probebly because I didn't setup Postfix right >(I use every thing default), I didn't get better performance than using >Sendmail.
We use sendmail and even with LDAP maps for everything (routing, virtuser, generics, aliases) performance is very good. Have you tried producing a strace summary of an sendmail process when delivering a message to see where it is spending all of its time. Possibly DNS is very slow? Or your DSA if using LDAP? I created a DNS slave and DSA replicant local on my mail server solely for use by the local services (sendmail, nss, etc...). You should probably head over the the sendmail lists/pages if the problem is your MTA.
