Email & PTR Issues

John Miller johnmill at
Tue Nov 7 18:00:39 UTC 2017

Hi James,

Having a PTR record for your IP address is sort of a baseline standard
that e-mail providers use to tell whether you're a spammer or not:
your forward and reverse DNS records must match up.  More
specifically, the FQDN that you provide in your SMTP EHLO must match
your forward and reverse DNS records.

If your mail server is EHLOing as, then you must have
a matching PTR record.  Doesn't look like you have one: the address
space belongs to your ISP:    3600    IN    SOA 21 10800 900 604800 7200

so you'll need to talk with them to resolve it.  If they don't support
PTR records, I'd suggest moving your mail server elsewhere: matching
DNS records is pretty much a requirement these days for running a mail


On Tue, Nov 7, 2017 at 10:31 AM, James Pifer <jep at> wrote:
> Hello. I'm looking for help with an issue I've been fighting for some time.
> Background:
> Running BIND 9.9.
> Forwarding UDP & TCP Port 53 through firewall.
> I have issues emailing to certain domains. I use my own mail server to
> deliver mail. It is currently not sending through SMTP Relay. The failure
> says that I have a missing PTR record. For example:
> host[]
>     said: 550 5.7.1 Connections not accepted from servers without a valid
>     sender domain.alph151 Fix reverse DNS for (in reply to
>     FROM command)
> If I do a test on mxtoolbox it also says I have the issue:
> If I look at dnsstuff and do a test on Mail Server Test Center and run
> selected tests under the MX Dashboard it gives a DNS Mismatch.
> BUT, If I look at dnsstuff,com and do a reverse lookup test, that seems
> successful:
> Also, from a pc somewhere else on the internet, if you change your DNS
> server to mine (or use nslookup) it resolves the reverse entry ok.
>> server
> Default Server:  []
> Address:
> Server:  []
> Address:
> Name:
> Address:
> If anyone has any helpful suggestions it is appreciated.
> I also tried moving my DNS to the provider I purchased my domain name from
> thinking that would be an easy fix. They don't support PTR records and
> actually had no clue what they even were.
> I've also tried configuring my mail servers to use ATT's SMTP Relay, but so
> far I've been unsuccessful getting it to send at all. The emails keep
> getting deferred. Obviously not an issue for anyone on this list. Just
> providing info.
> Thanks
> James
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John Miller
Systems Engineer
Brandeis University
johnmill at
(781) 736-4619

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