SMTP Reverse DNS Mismatch Warning – Reverse DNS does not match SMTP Banner

This alert on an SMTP check on Mxtoolbox is trivial.

It could be because your outbound (sending) mail server is blocking un-authenticated port 25 use by spammers. Instead you can authenticate (login) on port 487 to send email.

This from Mxtoolbox:

“Also, the banner mismatch is just a warning. There’s nothing that says that having a mismatch (or no hostnme in your banner at all) will cause you to have difficulty sending or receiving mail, it’s really more of a best practice.”

Find DNS server records mx cname ttl A record rDNS

Easily find your nameserver’s records including a, mx, cname and ttl for each:

My favorite overall DNS testing tool for 2012 is, which will also show your rDNS record.

How to tell if your website has a dedicated IP

Email bounces – creating SPF records and rDNS

If your hosting account does not have a correct Reverse DNS entry some receiving email servers may reject your email because of this. It is something generic which some mail servers to check for. You can sort this properly a couple of ways…

Update the Reverse DNS for that IP to match the A record you created earlier or if ask your hosting company to do it.

Ask your ISP or hosting company if you can forward your outbound email to one of their mail servers..called a relay server.

You should also make an SPF record for your domain. Read more here:

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