Hi guys

I have to look at ways to resolve an issue that has been raised by a customer all because of emails they send to specific people who use surfcontrol on their email servers and report that the mail is coming from a spoofed address.  Apparently the server is doing a revers lookup on the IP and it doesn't match their domain name as it resolves to the default domain.

The only way i can see to resolve this is to get a revers IP address to resolve to a specific IP address that we set aside for this customer.  so that if the servers do do the reverse ip lookup it gets the correct domain name associated.  This is simple enough however how do you get the sending smtp server to use the correct IP address for sending mail from that users account/domain. Especially when we have multiple smtp servers.  The only way i have thought of being able to try this is using the ISA firewall and creating some kind of rule but can't see it being easy. 

I am running the 3.0 solution in this scenario and haven't had this problem with any other customer.  I personally don't think this is the real problem but you have to try and give the customers what they want.  I am sure others have encountered this problem as it would just be hosted exchange this would be all mail platforms.

I also can't see everyone setting up ip address for every single domain that they host for either especially if we don't host the domain records.

A method that may work is to create separate outbound SMTP connectors for each company that needs this capability.  Then create security groups for those companies an only allow those groups to access the SMTP connector.  This may have an impact on your scalability and performance as the system will have to look up the group membership for each outbound e-mail.  This performance hit can be mitigated by keeping the group membership flat (no nested groups).

Thanks