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RDNS CNAME for MX Record Issue

Okay, so I'm not sure if this is by design or if it is indeed an issue. Just encountered a third-party that's using a CNAME for their MX PTR record and the UTM (9.209-8) rejects it with "RDNS invalid".

"Dig" returns a valid response and checking their domain on various DNS validation sites, everything reports "OK" with their MX and PTR setup.

From what I can gather, it's generally considered "not the best" to use CNAMEs for MX PTR records but there also doesn't appear to be any hard and fast RFC rules that forbid it. So, on to my question; do I just deal with it and create an exception for these people or is this something that should go into a "feature request" list or is this a bug that needs to be fixed?

Thanks!

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0 GoAboutYourBusiness over 10 years ago
Hi Bob, yes 'Strict RDNS' is selected (I already had some internal debate on that topic due to the overwhelming amount of ill-informed admins out there; not that RDNS is the end-all be-all of anti-spam measures, but that's another discussion. When 68% of your inbound mail is spam and 18% of that is stopped by RDNS checks, every little bit helps as far as I'm concerned).

The log just shows 'extra="RDNS invalid"' and 'Invalid RDNS entry for 12.226.35.114':

/var/log/smtp.log:2014:11:18-12:56:53 pututmp01 exim-in[22430]: 2014-11-18 12:56:53 id="1003" severity="info" sys="SecureMail" sub="smtp" name="email rejected" srcip="12.226.35.114" from="foo.bar@millenniumpartners.net" to="foo.bar@putnam-fl.com" size="7360" reason="rdns_helo" extra="RDNS invalid"
/var/log/smtp.log:2014:11:18-12:56:53 pututmp01 exim-in[22430]: 2014-11-18 12:56:53 H=(mail.millenniumpartners.net) [12.226.35.114]:36609 F= rejected RCPT : Invalid RDNS entry for 12.226.35.114
/var/log/smtp.log:2014:11:18-12:56:53 pututmp01 exim-in[22430]: 2014-11-18 12:56:53 SMTP connection from (mail.millenniumpartners.net) [12.226.35.114]:36609 closed by DROP in ACL

So like I said, I'm not sure if it's just the fact that the UTM doesn't like the CNAME and/or whether or not this should be a bug report or a feature request or something else.

Thanks!
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0 GoAboutYourBusiness over 10 years ago
Hi Bob, yes 'Strict RDNS' is selected (I already had some internal debate on that topic due to the overwhelming amount of ill-informed admins out there; not that RDNS is the end-all be-all of anti-spam measures, but that's another discussion. When 68% of your inbound mail is spam and 18% of that is stopped by RDNS checks, every little bit helps as far as I'm concerned).

The log just shows 'extra="RDNS invalid"' and 'Invalid RDNS entry for 12.226.35.114':

/var/log/smtp.log:2014:11:18-12:56:53 pututmp01 exim-in[22430]: 2014-11-18 12:56:53 id="1003" severity="info" sys="SecureMail" sub="smtp" name="email rejected" srcip="12.226.35.114" from="foo.bar@millenniumpartners.net" to="foo.bar@putnam-fl.com" size="7360" reason="rdns_helo" extra="RDNS invalid"
/var/log/smtp.log:2014:11:18-12:56:53 pututmp01 exim-in[22430]: 2014-11-18 12:56:53 H=(mail.millenniumpartners.net) [12.226.35.114]:36609 F= rejected RCPT : Invalid RDNS entry for 12.226.35.114
/var/log/smtp.log:2014:11:18-12:56:53 pututmp01 exim-in[22430]: 2014-11-18 12:56:53 SMTP connection from (mail.millenniumpartners.net) [12.226.35.114]:36609 closed by DROP in ACL

So like I said, I'm not sure if it's just the fact that the UTM doesn't like the CNAME and/or whether or not this should be a bug report or a feature request or something else.

Thanks!
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