Recipient account not found
Check the recipient address or account state.
What to do now
- Check the recipient address for typos.
- Confirm that the account is currently in use.
- If the address is correct, contact the recipient another way to confirm the account state.
Representative reply
550 5.1.1 User unknown
Retry decision
If the address or account state is responsible, retries alone may not resolve it. Check the recipient address first.
Why it happens
An address typo, deleted account or inconsistent recipient directory may be responsible.
Typical stage
RCPT TO
- CONNECT
- EHLO
- MAIL FROM
- RCPT TO
- DATA
- DELIVERY
Stages vary by server. Confirm the actual stage from the complete reply and session logs.
What is SMTP Reply Code?Open only the explanations you need
Three-digit server reply: 4xx is transient, 5xx permanent. Read the complete text to investigate the cause.
What is Enhanced Status Code?Open only the explanations you need
An extended status such as 5.1.1. Server wording and usage may vary.
What is RCPT TO?Open only the explanations you need
SMTP command identifying a recipient.
What is MX?Open only the explanations you need
DNS record identifying receiving mail servers for a domain.
Check directly
- Check the recipient address for typos.
- Confirm that the account is currently in use.
- If the address is correct, contact the recipient another way to confirm the account state.
If you operate or diagnose the mail server, the tools below can help with these checks.
dig MX example.com openssl s_client -starttls smtp -connect mx.example.com:25 -verify_return_error -crlf EHLO test.example MAIL FROM:<sender@example.com> RCPT TO:<user@example.com>
Cautions
Observed DSNs do not map one-to-one to causes. The stage shown is typical; confirm it with the full reply and actual logs.
Similar reply wording and observed status codes
no such useruser unknownrecipient unknownunknown useraddress unknownuser not foundno mailbox hereno mail-box hereno such recipient here
Observed DSNs: 5.1.1, 5.5.1, 5.5.0, 5.5.3