Comcast

4.2.0

This Comcast recipient is temporarily unavailable. Retry with backoff. Suppress only if it never recovers.

4.1.1

This Comcast mailbox received too many recent messages. Wait and retry at a lower rate.

4.1.1-2

This Comcast mailbox is over quota. Retry later, or ask the recipient to free space.

5.1.1

Comcast says this is not their customer. Treat it as a hard bounce and remove the address.

5.1.1-2

Comcast says this mailbox is unallocated. Treat it as a hard bounce and remove the address.

5.2.0

Comcast rejected this under DMARC. Align SPF or DKIM with the From domain so DMARC passes, then resend.

5.2.0-2

Comcast says this recipient is unavailable. Verify the address. Suppress it if it keeps failing.

5.1.1

Comcast rejected this recipient for an extended quota violation. Retry later, or ask them to free space. Suppress if it never recovers.

1

Comcast requires a valid PTR reverse DNS record on the sending mail server. Fix reverse DNS, then resend.

2

Comcast blocked this IP for spam. Review postmaster guidance, clean reputation, and request delisting before sending again.