Question : Reverse DNS A record IP address

Hello,
I'm not that familiar with reverse dns so I need some help.  We have an in-house exchange server with two static ip dsl lines on a load-balancer (not a lot of load, mainly for failover protection).  All incoming emails go through our spam service, so exchange is locked to receive from their ip's only, nothing direct to the dsl ip's.  I've got DNS hosted on a third-part service so we can control it.  The MX records point to the spam service (let's say mail.spamservice.com), and our web A record (mydomain.com) points to a dedicated web server hosted by another company and does no email processing.   My question is regarding our outgoing emails from our in-house exchange server.  It is named mail.mydomain.com.  I've had the ISP's for both our dsl lines set the ptr record to mail.mydomain.com, so they match the exchange server name.  We do not use mail.mydomain.com for anything as nothing can access our exchange server directly.  What should the A record IP address be for mail.mydomain.com, or does it even matter since the name will match the exchange server name?  My only concern here is that we're not rejected by AOL and the like.  Should it be the dsl line ip address?  If so, half the time it will be wrong if the mail goes out the other line.  Thanks for any help.

Answer : Reverse DNS A record IP address

Sorry - I don't know what I was thinking...I forgot that you don't have an A record for the second IP address.  That's what I would recommend - create a second host record for your domain (i.e., mail2.m-depot.com) and point that to your second IP address.  That way, whichever IP is used to send the mail, it will resolve correctly. It will have a slight hiccup when it sees that the banner for your Exchange server is "mail.m-depot.com" instead of "mail2.m-depot.com" but I don't think the email will be rejected because of that.