Hi All: Is there any way to force the SMTP service to use a particular IP when sending mail? I've found that even if you bind the SMTP service to a particular IP, it will listen on that IP, but it won't actually send email from that IP (if you have more than one IP address bound to a NIC). It appears to use "any available" IP that isn't bound to a specific website or SMTP service.
In IIS6, the behavior was similar but more predictable...no matter what IP you bound the SMTP service to, it would always send on the first IP bound to a NIC.
Just wondering if I'm missing something obvious, or if there's a registry hack or something that can force SMTP to a particular IP?
The reason I'm asking is because on a server with multiple SMTP services, each bound to a particular domain name/IP, when the receiving server does a reverse-lookup of the IP of the SMTP service, it will return a PTR name that is not the same as the EHLO (for a different domain entirely), and while there's nothing in the RFCs that says that's a problem, a lot of anti-spam devices will misinterpret that as a trojaned machine and block mail, or increase it's spam score.
I've found it increasingly difficult to prevent large ISPs from blocking mail when this happens.