Sending email from a different domain than the mail server's rDNS

Question

We have a dedicated server for hosing our email, we'll say the IP address for this server is 1.1.1.1.

The rDNS is set to mail.xxxxx.com (this is the MX recored of xxxxx.com and has an A record pointing to 1.1.1.1).

We also host email for some clients, such as yyyyy.com, who has an MX record of mail.yyyyy.com (A of mail.yyyyy.com record pointing to 1.1.1.1).

When we send emails from our ASP.NET sites we use mail.xxxxx.com as the mail server and use a specifically setup login. We use these settings regardless of the from address, it could be info@xxxxx.com or info@yyyyy.com.

Does it matter that we're sending emails with a from address of info@yyyyy.com from a mail server of a different domain mail.xxxxx.com, but it does have the same IP?

Thanks for any input!

Answer 1

This is fairly normal, the only thing I'd be concerned about is using the same IP as the clients. If you trust the clients then it's not an issue. However, if you don't I would suggest obtaining more IP addresses in case your customers get yours blacklisted.

On the domain side of things it shouldn't make a difference. To be doubly sure you can add a SPF record for each domain to show that the domain is allowed to send email from this IP address.