I have a Windows Server 2008 system I am using for web site and application hosting. I use Plesk for our web site hosting which uses the MailEnable SMTP server for our domains outgoing mail. We also have a newsletter application that uses Microsoft's SMTP server as it's outgoing mail server. To make sure that neither use can negatively affect the other with regard to spam blacklists etc. (our newsletter is opt-in and we go out of our way to stay on the right side of the moral street, but from time to time our hosted domains will run into trouble that we have to clean up.)
The Microsoft SMTP is bound to our secondary address on 192.x.x.253 and the MailEnable server is bound to our primary: 192.x.x.252. They both work fine and I can connect properly to either one. When the Microsoft SMTP server sends outgoing mail though, the headers report that it is going out on the primary IP address 192.x.x.252 rather than the one it is bound to, 192.x.x.253.
I have seen this Server Fault question: IIS Virtual SMTP to use the secondary IP when sending email that is very similar, but the solution they came up with was to use a firewall rule to redirect ALL SMTP traffic to the secondary IP.
Is there any settings I can add to Microsoft's SMTP so that it sends all outgoing mail on the secondary address? If not, are there any decent free SMTP servers you can recommend that would be able to do this?
My fallback is to modify MailEnable to send on the secondary IP, but I would rather modify the settings there because I don't want to tweak anything related to the Plesk integration if I don't have to.
