Email and Reverse Lookup Problems

550 IP address does not properly resolve for reverse DNS lookup
Or
<mail server name>#smtp;501 5.7.1 <sender's email address>...Sender IP must resolve

If you received an error message similar to one of the above in response to an email you sent, then there is a problem with your email server and its DNS configuration.

Your mail server may have an invalid DNS name. When setting up the mail server, you should identify it by its fully qualified domain name. In Veraciti's case, for example, our main mail server is called smtp01.kooobra.com, and that's the name with which it identifies itself. Supplying this name indicates that you are really who you say you are. In order for this to work, your mail server must have a valid DNS A record for the server. You can then look up this mail server address on the Internet to determine if it is valid

Next in order to check the validity of the mail server address, the mail software uses a technique called a reverse lookup. The software supplies an IP address for your mail server and it expects a list of names back. You set this up with DNS PTR records. If you don't have reverse DNS PTR record, or if the address doesn't match your mail server name, we will not accept your mail.

Why are we doing this?

It's possible that you will now say: "But this isn't our fault. Our mail goes everywhere with no problems, only you reject it. You must be doing something wrong''.
We contend that we're doing something right. Currently, the Internet is overrun by by individuals who use email inappropriately and in some cases, illegally. Currently, state, national and international laws have not been able to come to terms with the problem. The message above, for example, was generated in response to an attempted spam delivery, and the lack of correct DNS information is a popular technique to hide the identity of the sender. A lot could be done simply by adhering to the standards, which is what we're doing.

Often, there are legitimate mail servers out there which are set up incorrectly. If you received one of these messages from us, it means we believe you are a legitimate user and we encourage you to adhere to the standards by properly configuring your DNS.