PUBLIC MARKS from camel with tags mail & smtp

The original qmail-smtpd accepts by default all messages, checking later for the existence of recipients. So, if the message is delivered to not existing recipients, a lot of additional system work and network traffic are generated, with multiple expensive bouncing if the sender is a fake one. chkuser has been developed with the goal to improve the acceptance SMTP phase of qmail-smtpd. qmail-smtpd patched with chkuser may check the existence of e-mail recipients immediately in the SMTP acceptance phase of a message and rejects instantly all messages not directed to existing users, avoiding additional traffic, work and messages bounced more times.

To test and benchmark several common SMTP servers for Unix. This is inspired by the work done by Matthias Andree at his Postfix vs. qmail - Performance page. His information, while likely still highly relevant is based heavily around file system I/O and not overall performance of the MTA. Additionally, more MTAs and OSs will eventually be tested here.