Added the new datacenter's name servers to /etc/resolv.conf

Changed myhostname in /etc/postfix/main.cf

Added stream.radiosai.org CNAME domain record in Plesk

Added the gmail account to the mailer daemon's list of addresses

Found lots of errors in /var/log/mail.err - fatal: open database /etc/aliases.db: No such file or directory
Ran newaliases and restarted postfix as per http://www.howtoforge.com/forums/showthread.php?t=652

Restarting postfix in debian (not service postfix restart as in RH/Mandrake): command is
/etc/init.d/postfix restart