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Reverse DNS is not a valid Hostname
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My ISP has a PTR record set to domain.com. My mail host name is, mail.domain.com. Testing DNS at mxtoolbox gives an error, "Reverse DNS is not a valid Hostname." I do have Oracle DNS. It has two A records, one is domain.com pointing to server ip address, and one is mail.domain.com pointing to the same server address. There is no PTR record in Oracle DNS. Everything else tests good except this reverse dns entry. Any recommendations would be appreciated.
Thanks,
jay
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Tyler Staff
@Jay
In this case, you would want to contact your ISP and have them change the domain value of the PTR record to mail.domain.com.
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If I do that will it mess up my other records that are set to domain.com in DNS?
Thanks,
Jay
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Tyler Staff
@Jay
Is the IP address associated with the PTR record being used for anything else other than MDaemon, like a website? Perhaps it's not necessary to change the PTR. For example, MDaemon's default reverse lookup configuration will not reject SMTP sessions for PTR mismatches and/or if no PTR is found. However, an email server with stricter requirements may require the PTR matches the hostname used by the sending server or that a PTR actually exists.
Either that or change the hostname MDaemon uses from mail.domain.com to domain.com. Select Setup > Domain Manager > [domain.com] > Host Name & IP and edit the SMTP Host name text box.
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No that ip address is only for the mail server. I did have the host name as domain.com at one point but I was still getting that invalid host name error. I believe I also had problems with Let's Encrypt until I changed the host name, as well. I will ask Comcast to change the PTR as you suggest and see how it works.
Thank you for your help,
Jay
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@TylerComcast added PTR for mail.domain.com and all is green on mxtoolbox for the first time.
Thank You!
Jay
