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I have a single server with single ip running a web server, mail server and bind (all for a single domain).

In my DNS zone file I created A records for,, and ("frog" being my hostname). All of these records point to the same ip address.

In the reverse zone file I have a PTR record pointing to

So far so good, but now I am reading that some email spam protection are doing reverse DNS lookups to check for ip spoofing (as far as I understand).

Does this mean that I have to change my reverse PTR record to point to instead of in order to pass the spam filters?

If yes, could this have any negative effect on my web server or DNS?

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If your mail server identifies itself as, that should be what your PTR record has. It is perfectly fine, for your mail server to identify itself as when sending and receiving mail. You have an A record for, and that is the address which will pass rDNS validation. Given your pointer record, you should configure your mail server to identify itself as

You can leave your MX record pointing to as mail servers shouldn't be verifying the name of the server they are sending to.

Most legitimate mail servers pass rDNS validation, as yours will when using

Consider setting up SPF records to protect your domains. Domains not sending mails should have a policy which prevents their use by mail servers or as sender domains. In your case I would allow mail from and, and not allow mail from If you are using as convenience to access your mail server to send and receive mail, then I would consider not allowing it to send mail. (Mail will originate from

You could change your PTR record to, which is a more traditional server name. In that case, I configure SPF to prevent mail from, and allow it from

Once you get this working to your satisfaction, look into adding DKIM and DMARC functionality.

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