I'm having a similar problem that is a MAJOR issue because we're ending up blocked by some servers since all our records don' match up. We have a dedicated server, with the main IP being 116, and maindomain.com. We have a mailserver on 118, that is seconddomain.com. when we send mail from second domain, it will frequently bouce back (From Sprint & Verizon and a few others) with an error that says
"SMTP error from remote ,ail server RCPT TO:..... 550<mail.maindomain.com> Client Host Rejected: Access Denied"
It appears that the server recieving it thinks it's being send by maindomain.com iinstead of seconddomain.com.
RDNS is set up, DNS is being hosted on ZoneEdit.com, and seem sto be all configured correctly. The only thing I can thin of is we're missing something on the server. PLEASE HELP!