Comcast

smtp;450 4.2.0 <example@comcast.net> - Recipient temporarily unavailable

Low severity

smtp;452 4.1.1 <example@comcast.net> too many recent messages; Try again later

Low severity

smtp;452 4.1.1 <example@comcast.net> user over quota

Low severity

smtp;550 5.1.1 Not our Customer

Low severity

smtp;550 5.1.1 <example@comcast.net> recipient mailbox unallocated

smtp;550 5.2.0 Message rejected due to DMARC. Please see http://postmaster.comcast.net/smtp-error-codes.php#DM000001

High severity

smtp;550 5.2.0 <example@comcast.net> - Recipient unavailable

smtp;552 5.1.1 <example@comcast.net> recipient rejected - extended quota violation

host xx.comcast.net [x.xx.xx.xx] SMTP error from remote mail server after initial connection: 554 xx.comcast.net comcast x.xx.xx.xx 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

Low severity

554 xx.comcast.net comcast x.xx.xx.xx Comcast block for spam. Please see http://postmaster.comcast.net/smtp-error-codes.php#BL000000

Low severity