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PTR records, comcast will not accept our email

We use our own email server and our PTR was setup by Comcast_Jon a while back. It was working fine until today. As far as I can tell we are emailing everyone but comcast. 

 

dig -x "ipaddress" returns correct from local DNS. DNS checking from Mxtoolbox and dnsqueries show PTR is fine too.I see no errors at all, other than a return mail coming from comcast stating why our mail is not accepted. if anyoneone at tech support staff could check our PTR records for correctness and confirm please. thanks

 

Comcast requires all sending mail server IP addresses have a valid PTR record set up. This error results when the lookup failed. NXDOMAIN response. One of the authoritative servers for the relevant section of the in-addr.arpa DNS tree is saying that there is no PTR record for the given IP address.


    (reason: 554 resimta-po-02v.sys.comcast.net comcast 2601:58a:8102:3e00:213:d4ff:fe10:2538 Comcast requires th... requirement. For more information, refer to: )

   ----- Transcript of session follows -----
... while talking to mx2.comcast.net.:
<<< 554 resimta-ch2-24v.sys.comcast.net comcast 2601:58a:8102:3e00:213:d4ff:fe10:2538 Comcast requires that all mail servers must have a PTR record with a valid Reverse DNS entry. Currently your mail server does not fill that requirement. For more information, refer to:
... while talking to mx1.comcast.net.:
<<< 554 resimta-po-02v.sys.comcast.net comcast 2601:58a:8102:3e00:213:d4ff:fe10:2538 Comcast requires that all mail servers must have a PTR record with a valid Reverse DNS entry. Currently your mail server does not fill that requirement. For more information, refer to:
554 5.0.0 Service unavailable

    (reason: 554 resimta-ch2-07v.sys.comcast.net comcast 2601:58a:8102:3e00:213:d4ff:fe10:2538 Comcast requires t... requirement. For more information, refer to:

   ----- Transcript of session follows -----
... while talking to mx1.comcast.net.:
<<< 554 resimta-po-20v.sys.comcast.net comcast 2601:58a:8102:3e00:213:d4ff:fe10:2538 Comcast requires that all mail servers must have a PTR record with a valid Reverse DNS entry. Currently your mail server does not fill that requirement. For more information, refer to:
... while talking to mx2.comcast.net.:
<<< 554 resimta-ch2-07v.sys.comcast.net comcast 2601:58a:8102:3e00:213:d4ff:fe10:2538 Comcast requires that all mail servers must have a PTR record with a valid Reverse DNS entry. Currently your mail server does not fill that requirement. For more information, refer to:
554 5.0.0 Service unavailable

    (reason: 554 resimta-po-06v.sys.comcast.net comcast 2601:58a:8102:3e00:213:d4ff:fe10:2538 Comcast requires th... requirement. For more information, refer to:

   ----- Transcript of session follows -----
... while talking to mx2.comcast.net.:
<<< 554 resimta-ch2-11v.sys.comcast.net comcast 2601:58a:8102:3e00:213:d4ff:fe10:2538 Comcast requires that all mail servers must have a PTR record with a valid Reverse DNS entry. Currently your mail server does not fill that requirement. For more information, refer to: http://postmaster.comcast.net/smtp-error-codes.php#554
... while talking to mx1.comcast.net.:
<<< 554 resimta-po-06v.sys.comcast.net comcast 2601:58a:8102:3e00:213:d4ff:fe10:2538 Comcast requires that all mail servers must have a PTR record with a valid Reverse DNS entry. Currently your mail server does not fill that requirement. For more information, refer to:
554 5.0.0 Service unavailable

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Re: PTR records, comcast will not accept our email

I believe you may be having the same problem as the user in this post:

 

http://forums.businesshelp.comcast.com/t5/IPV6/Google-mail-requires-IPv6-PTR-record-but-Comcast-does...

 

Take a look at the SMTP error messages you posted. Notice how they all refer to IPv6 addresses? From here, it looks like your mail server may be receiving a dynamic IPv6 address from the Comcast modem, and is successfully trying to use it. However, that IPv6 address does not have a PTR, as it is dynamic (like all other IPv6 addresses on Comcast's network today.)

 

You will need to wait for static IPv6 addresses before you can get a PTR added. If your mail server is not automatically falling back to IPv4, for the time being you will need to prevent your mail server from using IPv6.

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Re: PTR records, comcast will not accept our email

Good morning,

 

Comcast_Jon confirmed yesterday my PTR records weren't corrupt.

also online tests gave also good results. besides my server IPV6 has always been disabled, and it always worked that way.

 

train_wreck, that link you provided made me realize there had to be further tweaks? so I did a search online and found a reference to also disable the reference to the IPV6 loopback on the hosts file, and that did it.

 

it seems a recent update may have expanded how the server looks for an IPV6 address. it all well now again, than you.

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Re: PTR records, comcast will not accept our email

not quite done yet, I ran

 

echo 1 > /proc/sys/net/ipv6/conf/all/disable_ipv6
echo 1 > /proc/sys/net/ipv6/conf/default/disable_ipv6

which adds

 

net.ipv6.conf.all.disable_ipv6 = 1
net.ipv6.conf.default.disable_ipv6 = 1

 

 

solved.

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Re: PTR records, comcast will not accept our email

Yes, those sysctl entries disable IPv6 completely for all network adapters on Linux.

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