Question about DNS - forward and reverse

[Dollie]

When a mail server does 'reverse dns' when deciding to allow or deny an email, does it compare MX records (ie. mail.abc.null), or does it look at the A record for the domain itself (abc.null)?

Does the reverse DNS of the mail server need to match that of the website (

http://www.abc.null)

or the domain?

I think I asked that the right way...

 

[cajuntank]

It looks at what's called a PTR record to see if that IP address matches the name of the server that sent out the mail.

So for example (you'll see this a lot on cable and DSL accounts), you could have a host and mx record for your mail server that is mail.domain.com and your ISP have a PTR record for your static IP address (the one nat'd to your mail server) of something like 72-169-52-34.adsl.isp.net
This will cause problems with a lot of servers you try to send mail to since the names don't match. Your ISP, not necessarily your DNS provider, should be change that for you fairly easily and again, it needs to match your sending mail server as it is named on the internet.

You can use any DNS provider to host your name records to point to your assigned static IP addresses for your hosts, but only the ISP who you are connected to, can change the name of the PTR record(s) for the IP addresses they assign.

Hope I could help.

 

[exch2007]

You should get your isp to change the reverse dns name of your ip to that of your mailserver which would resolve this issue with hotmail, yahoo, google mail etc.

You can check your reverse dns ip name here as well.

http://mxtoolbox.com/diagnostic.aspx

 

[58sniper]

In a perfect world, your MX records, rDNS record, and banner would be the same name. When that's not the case, the rDNS and banner should match.

Pat Richard
Microsoft Exchange MVP
Contributing author Microsoft Exchange Server 2007: The Complete Reference

 

[58sniper]

Oh - forgot to add that technically, it's an RFC violation to refuse mail when the rDNS entry is incorrect.

Pat Richard
Microsoft Exchange MVP
Contributing author Microsoft Exchange Server 2007: The Complete Reference