5.3.0 other mail system problem 554 '5.4.12 smtp

A SMTP error!

The error message 554 5.4.12 SMTP is a generic error code that can have various causes. Here's a breakdown of the error code:

• 554: This is the SMTP response code, which indicates that the message was not delivered.
• 5.4.12: This is the specific error code, which is a sub-code of the 5.4 range. The 5.4 range typically indicates a "mail system problem" or "delivery failure".

The 5.4.12 error code specifically indicates that the recipient's mail system is not accepting the message. This can be due to various reasons, such as:

1. Recipient's mailbox is full: The recipient's mailbox may be full, and the mail system is refusing to accept new messages.
2. Recipient's email address is invalid: The recipient's email address may be invalid, or the domain may not exist.
3. Recipient's mail system is down: The recipient's mail system may be experiencing technical issues, such as a server outage or maintenance.
4. Spam filtering: The recipient's mail system may be blocking the message due to spam filtering rules.
5. Firewall or network issues: There may be firewall or network issues that are preventing the message from being delivered.

To troubleshoot this issue, you can try the following:

1. Check the recipient's mailbox: Verify that the recipient's mailbox is not full and that the email address is valid.
2. Check the recipient's mail system: Verify that the recipient's mail system is functioning correctly and that there are no known outages or maintenance issues.
3. Check your email settings: Verify that your email settings are correct and that you are not sending emails to invalid recipients.
4. Check for spam filtering issues: Verify that your email is not being flagged as spam by the recipient's mail system.
5. Contact your email provider: If you are still experiencing issues, contact your email provider's support team for further assistance.