Email provider
Comcast SMTP Error Codes and Bounce Messages
Comcast, branded Xfinity, gives comcast.net mailboxes to its internet customers. Accounts go inactive after roughly 90 days without a sign-in, so these addresses age out over time.
- Codes on record
- 5
- Responses
- 10
- Domains
- comcast.net
Postmaster & documentation
SMTP 4501 response
A temporary problem. The sending server keeps retrying for a while, and delivery often recovers on its own once the underlying issue clears. See SMTP 450 across every provider
SMTP 4522 responses
A temporary problem. The sending server keeps retrying for a while, and delivery often recovers on its own once the underlying issue clears. See SMTP 452 across every provider
SMTP 5504 responses
smtp;550 5.1.1 Not our Customer
smtp;550 5.1.1 <[email protected]> recipient mailbox unallocated
smtp;550 5.2.0 Message rejected due to DMARC. Please see http://postmaster.comcast.net/smtp-error-codes.php#DM000001
smtp;550 5.2.0 <[email protected]> - Recipient unavailable
A hard failure. The receiving server has refused the message for good and will not accept an unchanged retry without a change on the sending side. See SMTP 550 across every provider
SMTP 5521 response
A hard failure. The receiving server has refused the message for good and will not accept an unchanged retry without a change on the sending side. See SMTP 552 across every provider
SMTP 5542 responses
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
554 xx.comcast.net comcast x.xx.xx.xx Comcast block for spam. Please see http://postmaster.comcast.net/smtp-error-codes.php#BL000000
A hard failure. The receiving server has refused the message for good and will not accept an unchanged retry without a change on the sending side. See SMTP 554 across every provider
Comcast bounce questions
›Why is Comcast bouncing my email?
Comcast, branded Xfinity, gives comcast.net mailboxes to its internet customers. Accounts go inactive after roughly 90 days without a sign-in, so these addresses age out over time. Match the exact wording of your bounce to one of the 10 responses on this page to find the specific reason and fix.
›How do I improve deliverability to Comcast?
Authenticate with SPF, DKIM and DMARC, keep your sending IP and domain reputation clean, mail only engaged recipients, and honour unsubscribes. Comcast also publishes postmaster guidance, linked on this page.
