You have a couple of choices in the mailer.
1: Send mail directly from Tornado to the destination host, based on MX records
2: Relay all mail to a single host
To relay through a single host, add the following to puakma.config
Omitting the above settings will tell the MAILER task to send mail directly to the destination.
'Connection reset' usually means the receiving host has dropped the connection. Perhaps relaying is not allowed from the address you are at?