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Here is the scenario:<br />
mail.domain.com is hosted to IP 1.2.3.4 inbound at serverX(which is a SPAM filter front end), outbound mail comes from serverY(actual mail server) at IP 5.6.7.8 for<u> same domain</u>. Incoming has no issues since MX and RDNS reflect IP 1.2.3.4, but outbound has some issues when the server receiving the e-mail at anothermail.anotherdomain.<wbr />com checks the IP and sees RDNS at IP 1.2.3.4 coming from server IP 5.6.7.8. <br />
My options include:<br />
1)pointing outbound mail via smart host to 1.2.3.4 and all would be good, but am having issues getting that to work.<br />
or<br />
2)Changing name of server at 5.6.7.8 to mail2.domain.com and creating another RDNS for it. Not sure if MX is required for outbound or if anything else also needs to be done.<br />
<br />
Sueggestions/Questions?
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Here is the scenario:
mail.domain.com is hosted to IP 1.2.3.4 inbound at serverX(which is a SPAM filter front end), outbound mail comes from serverY(actual mail server) at IP 5.6.7.8 for same domain. Incoming has no issues since MX and RDNS reflect IP 1.2.3.4, but outbound has some issues when the server receiving the e-mail at anothermail.anotherdomain.com checks the IP and sees RDNS at IP 1.2.3.4 coming from server IP 5.6.7.8. 
My options include:
1)pointing outbound mail via smart host to 1.2.3.4 and all would be good, but am having issues getting that to work.
or
2)Changing name of server at 5.6.7.8 to mail2.domain.com and creating another RDNS for it. Not sure if MX is required for outbound or if anything else also needs to be done.

Sueggestions/Questions?

Multiple Mail Servers/IP's for one domain

Within Internet message handling services (MHS), a message transfer agent or mail transfer agent (MTA) or mail relay is software that transfers electronic mail messages from one computer to another using a client–server application architecture. A MTA implements both the client (sending) and server (receiving) portions of the Simple Mail Transfer Protocol (SMTP). The terms mail server, mail exchanger, and MX host may also refer to a computer performing the MTA function. The Domain Name System (DNS) associates a mail server to a domain with mail exchanger (MX) resource records containing the domain name of a host providing MTA services.

Email Servers

Networking software modules are interfaced with a framework implemented on the machine's operating system that implements the networking functionality of the operating system. The best known frameworks are the TCP/IP model and the OSI model. Systems typically do not use a single protocol to handle a transmission. Instead they use a set of cooperating protocols, sometimes called a protocol family or protocol suite.[9] Some of the best known protocol suites include: IPX/SPX, X.25, AX.25, AppleTalk and TCP/IP. Other protocols indirectly related to networking include the hypertext transfer protocol (HTTP) and its related technologies, Dynamic Host Configuration Protocol (DHCP), Domain Name Server (DNS) and other Internet protocols.