We have several domains being hosted on multiple servers. We are in the process of moving all the domains from the registrars authority to ours so we can manage the zone file for each domain. However, I've heard conflicting information about proper record setup for mail.
For the purpose of this discussion. Assume the following:
Domain A.COM, B.COM, C.COM
DOMAIN A.COM
A Record= MAIL 208.208.208.37
MX record= MAIIL.A.COM
Reverse PTR Record defined for 208.208.208.37 = FORWARD-1.A.COM
DOMAIN B.COM
MX Record: MAIL.A.COM (this reference is setup as a CNAME record )
DOMAIN C.COM
MX Record: MAIL.A.COM (this reference is setup as a CNAME record)
Here are the questions:
My MX record is mail.a.com for ALL MY DOMAINS. Only the A.COM domain has a reverse PTR record for our mail server (208.208.208.37) and it resolves to forward-1.a.com. (this is the hostname of the mail gateway which delivers mail for all of our domains).
1) When a recipient domain is looking up an IP record. Is the IP they are looking up the 1st IP in the email header or is it looking up IP address of the MX record of the sending domain?
2) If its the first IP of the email header, ALL of our outbound traffic from all of our domains are HIDING behind a NAT address. In essence they are all hiding behind the public interface of our firewall. Lets say 208.208.208.2. So when we send email from our web servers in the DMZ our email clients from exchange.... ALL Source headers when looked at from the recipient domain will always say mail is originating from 208.208.208.2 (this is the firewall public IP).
when I run DNS checking tools for reverse PTR records for mail. I always type in the IP address of our mail server responsible for sending mail (208.208.208.37) and it passes no problem as it has a reverse entry for it. However, IF the firewall public IP is being looked at as the originating IP it will fail as we don't want to publish or create a PTR record for our Firewall for obvious reasons.
3) For adding SPF records, I don't understand the wizards that I've come across in what they are truly asking for. Can someone tell me what my SPF record should look like if I have multiple servers "sending" outbound mail. I only have 1 MAIL GATEWAY that delivers all mail, but I have multiple servers that deliver it to the mail gateway for the actual delivery. So with that being said, can someone tell me what my SPF record should look like?
Thanks
