is there any reason NOT to point multiple domain MX records to a single IP?
for example, if i had:
each of these have MX records pointing to the same IP.
this outside IP NAT's to a proofpoint server configured with multiple domains. two of these domains are on the same inside server (abc.com and def.com). one of them is on a separate inside server (xyz.com).
would there be any issues with outbound delivery of email on the xyz.com server simply because of the multiple MX records pointing to a single IP?
a single PTR record does exist for the outside address (as it should). but is there a problem associated with reverse lookups on abc.com, def.com and xyz.com and they all point to the same IP?
we are facing this issue in my company right now. we already have (say) abc.com and def.com using a single IP, but the hosting company is telling us it's not good practice to do this.
it has been working all along, so we want to know why, but we're not getting a good answer.