Reverse DNS

DNS is short for Domain Name System. As the name reveals, it's a way of relating Domain Names to computers/servers. Every server on the internet is reachable by its IP address (which is a number between 0 and 4 billion). People in general can't remember these, that's why they invented a way to relate a domain to a server. It's just like a phone book. You look for, and you find the number of its computer and you're good to go. Reverse DNS is using it the other way around. Say I've got an IP address and I want to know to which domain it corresponds, for this, we use Reverse DNS.

So, what does this have to do with e-mail? If your mail server does not have reverse DNS (on its IP address), you're just a number. The receiving server cannot be certain you are who you say you are. (You can point your domain anywhere you like, but only the owner of an IP address can point it to a domain). Not having reverse DNS will make you look like a spammer.

Our system checks your records, and let's you know if your reverse DNS is appropriately set up. If not, it will dispense advice on how to do this.

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