Enhanced SMTP status code · RFC 3463 · IANA
2.1.5 Recipient address is valid
A success code: the address was accepted. It appears in delivery confirmations, not in errors.
- Class: Success
Class 2: delivery succeeded (RFC 3463 §3.1). This is a success or warning code, not an error.
- Subject: X.1 · Address
About the originator or destination address: syntax or validity. The sender can usually correct it and retry.
- Associated basic codes (IANA registry)
Have the whole error message?
Sources: RFC 5321 · RFC 3463 · RFC 3464 · IANA · Gmail · Microsoft 365 · read on 26 September 2026