Postfix sender-based alternate relay host

http://www.advogato.org/person/richdawe/diary.html?start=126
Spent some time generating a CA and self-signed certificate on moto.
Had to copy moto's CA cert over to go so that it could be trusted (smtp_tls_CAfile = /etc/pki/tls/certs/motocacert.pem)
Needed these on the "go" side:
relayhost = mail.example.net
smtp_sasl_auth_enable = yes
smtp_sasl_password_maps = hash:${config_directory}/smtp_sasl_passwd
smtp_sasl_security_options =

Created that file ${config_directory}/smtp_sasl_passwd
Created a matching user on the "moto" side
It works!

"timed out while receiving the initial server greeting" see:
http://dbraslavsky.blogspot.com/2007/12/timed-out-while-receiving-initial.html

for testing AUTH, requiring base64 encoded useids/passwords:
perl -MMIME::Base64 -e 'print encode_base64("secretstuffhere");'