PTR Issue When emailing

We are using cpanel, all our domains can not send email nor receive email.
We are getting the error
This message was created automatically by mail delivery software.

A message that you sent could not be delivered to one or more of its
recipients. This is a permanent error. The following address(es) failed:

[email protected]
host [173.194.223.27]
SMTP error from remote mail server after end of data:
550-5.7.1 [12.105.171.197 19] Our system has detected that this message is
550-5.7.1 likely suspicious due to the very low reputation of the sending
550-5.7.1 domain. To best protect our users from spam, the message has been
550-5.7.1 blocked. Please visit
550 5.7.1 for more information. 2-20020aca1102000000b003a37a2a2786si6413641oir.260 - gsmtp

Welcome to the Cloudflare Community. :logodrop:

While the error doesn’t specifically mention a missing PTR record, it can contribute to delivery decisions made by receiving servers. You cannot set a PTR for this IP in Cloudflare. You will need to request that ATT configure it for you.

There are other steps that you can take to aid in email delivery. The following Community Tutorial is a good staring point.

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We do have a dedicated fiber internet and we control our DNS

Are you referring to the child zone of in-addr.arpa that contains your /29 SWIP allocation? If you do control that, you don’t appear to have updated the value for that IP. That zone cannot be managed at Cloudflare as the IPs are allocated to AT&T from ARIN. You will need to update the PTR record in the DNS for that zone.

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so what format for the in-addr.arpa for the ip class /26 ?

You don’t have a /26, you have a /29. You need to coordinate this with AT&T. It’s not in Cloudflare and cannot be hosted in Cloudflare.

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