smtp;450 4.2.0 <[email protected]> - Recipient temporarily unavailable
The receiver deferred the message and points at a mailbox problem (missing, disabled, or full) (enhanced status 4.2.0). Use the wording above to pin down the exact fix.
Email provider · 4.x.x transient failure
Comcast SMTP 450 Errors: Every Bounce Response Explained
Every SMTP 450 response on record from Comcast (comcast.net), with the verbatim text, the enhanced status code, a severity rating and a plain-English fix.
The requested action did not happen because the mailbox was briefly unavailable, for example locked, busy, or lightly rate limited. The sending server keeps the message queued and retries it.
- Provider
- Comcast
- Code
- 450 (4xx)
- Responses
- 1
- Highest severity
- Low
Comcast SMTP 450 responses
Postmaster & documentation
Comcast SMTP 450 questions
›What does an SMTP 450 error from Comcast mean?
The requested action did not happen because the mailbox was briefly unavailable, for example locked, busy, or lightly rate limited. The sending server keeps the message queued and retries it. At Comcast, it is a temporary deferral that is retried automatically, and the specific reason is in the enhanced status code and message text of each response below.
›How do I stop Comcast from returning SMTP 450?
Match your bounce text to one of the responses below and follow its guidance. Recipient-side wording means fix the address. Authentication or reputation wording (SPF, DKIM, DMARC, blocklist) means fix your sending setup, and check Comcast's postmaster documentation.