SMTP error 554 signals a permanent email rejection (5xx) due to problems with the sender's credentials, content, or policy violations (phpmailer, jenkins). This often indicates definitive refusal based on server policies.

What triggers SMTP Error 554?

Common scenarios behind SMTP Error 554:

1. Policy Violations: The email content violates recipient server policies, containing spam, malware, or prohibited file types.
2. Blacklisting: The sender's domain or IP is blacklisted, triggering rejection.
3. Poor Sender Reputation: Previous violations or spammy behavior lead to a negative sender reputation, causing rejections.
4. Invalid Recipient Address: The recipient's email address ("RCPT TO" or "To:") is incorrect or doesn't correspond to a valid mailbox (phpmailer, jenkins).

What’s Causing This SMTP Error 554 In Your Servers?

Potential causes of SMTP Error 554:

• Review Content: Ensure message content complies with recipient server policies. Remove or modify anything flagged as spam or malicious.
• Check Blacklists: If blacklisted, delist your domain or IP and work on improving email reputation.
• Improve Reputation: Adhere to email best practices and avoid spammy behavior to rebuild sender reputation.
• Verify Recipient Address: Double-check that the recipient's email address is accurate and belongs to a valid account or mailbox (phpmailer, jenkins).

How to Resolve SMTP Error 554 - Step-by-Step Solution

1. Revise Content: Address potential policy violations in the email message to comply with the recipient server's policies.
2. Delist from Blacklists (if applicable): Take steps to remove your domain or IP from blacklists.
3. Enhance Sender Reputation: Implement practices that improve your sender reputation, like authentication and avoiding spam.
4. Confirm Recipient Address: Ensure the recipient's email address is accurate and belongs to a valid account or mailbox (phpmailer, jenkins).

SMTP Error 554 Examples

• "554 5.7.1 Content blocked due to policy violations. Email flagged as spam."
• "554 5.1.0 Sender's domain blacklisted for abusive behavior. Contact administrator for removal."
• "554 5.5.2 Invalid recipient address recipient@example.com. Check recipient details."
• "554 5.2.3 Sender's email address has a poor reputation. Correct sender behavior."

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