Why is my e-mail being returned with a “bad reverse hostname lookup” from Thunder.Net?
Your mail was rejected by Thunder.Net because your server or your ISP’s server does not identify itself. Spammers often neglect to set the “reverse hostname lookup” for servers they use, or try to spoof a different host name. They do this for an obvious reason – they don’t want you to know who they are. But it’s rather easily detected. If a legitimate system is operating this way, it is misconfigured and needs to be fixed by its owner/administrator. This method has never been sufficient alone to turn away all spams. But as part of a combination of anti-spam techniques, it is useful and does reject many hundreds of spams every day at our sites. This is why many mail servers require hosts to identify themselves. If you have a legitimate server whose mail is rejected this way, ask your support or system administrators to fix it. If you are an administrator for your site, you need to set a PTR record in your DNS corresponding to the reverse lookup of your A record. See RFC 1912 “Common DNS
