SMTP error 550 is a permanent or "5xx" error code returned by a mail server to indicate that the server is unable to deliver an email message to the recipient's address. This error signifies a permanent rejection of the message and is often used to indicate that the recipient's email address or domain does not exist, or that the message violates the server's policies.
What's Causing This Error?
SMTP error 550 can be caused by various reasons, including:
- Non-existent recipient: The recipient's email address provided in the "RCPT TO" command or the "To:" field of the email message does not correspond to a valid email account or mailbox.
- Invalid recipient domain: The recipient's email domain (e.g., example.com) does not exist, has expired, or has DNS (Domain Name System) issues.
- Policy violations: The server may reject the message if it violates its policies, such as sending spam, containing malicious content, or exceeding size limits.
- Blacklisting: The sender's domain or IP address may be listed on email blacklists, which can trigger SMTP error 550.
How to fix SMTP Error 550?
- Verify recipient's email address: Ensure that the recipient's email address is spelled correctly, is complete, and corresponds to a valid email account or mailbox.
- Check recipient domain: Confirm that the recipient's email domain is functioning correctly, does not have DNS issues, and is not expired.
- Review email content: Check the content of the email message for potential policy violations, such as spammy content, excessive attachments, or links to malicious websites.
- Remove from blacklists: If the sender's domain or IP address is blacklisted, steps should be taken to request removal from the blacklist(s) and improve email reputation.
SMTP Error Examples
Example 1: "550 5.1.1 email@example.com: Recipient address does not exist."
Example 2: "550 5.4.5 firstname.lastname@example.org: Domain name not found. Check recipient domain."
Example 3: "550 5.7.0 Message blocked due to policy violations. Content flagged as spam."
Example 4: "550 5.7.1 email@example.com: Sender's domain blacklisted for abusive behavior."