Usually, SMTP errors with the 5xx code indicate an issue from the client email server and not your SMTP service provider.
‘Error 551: User not local; please try <forward-path>’ is one such error, indicating an issue with the recipient’s email address or server configuration.
This error can lead to emails bouncing back to your SMTP server. The bounced email can be of two types: Soft bounce and hard bounce.
Soft bounce occurs if the recipient’s inbox is temporarily unavailable or full. On the other hand, hard bounce occurs when the recipient’s email address is invalid or the email server isn’t configured to receive emails.
Resolving the Error – Solution
Since this error originates from the client email server, it typically means your SMTP server is configured correctly. You just need to ensure no additional issues affect the email server.
Start by confirming that all recipient email addresses are valid and that each email has enough storage space. If an email is invalid, you should request a valid email from the recipient.
Another troubleshooting step is to confirm that the recipient’s email server is available and configured correctly to receive emails from external sources.