Spam related delivery errors

SMTP Error 450 4.7.1

SMTP Error 451 4.7.1

451 4.7.1 Greylisting in action, please come back in 00:02:00 [minutes]

This error is usually followed by "Please try again later." It is connected with the sender's server. It is usually caused by an anti-spam policy or by a bad automatic update from antivirus software.

To fix the error, contact the SMTP service provider you use.

Requested action aborted — Local error in processing

A remote antispam filter might reject your request. Also, your internet provider may be overloaded, or too many emails were sent through your SMTP relay. The next attempt may be successful if the error still occurs — contact your SMTP provider.

Usually, the recipient's spam-filter sends this error for policy reasons, labeling your email as spam.

You can eliminate this error by asking a recipient to whitelist you.

551 Sender address is not valid for your login

551 This mail server requires authentication before sending mail from a locally hosted domain

Sometimes this error occurs intending to thwart spam, but it is not always accurate. To solve this problem, contact your internet service provider to ensure that you are a certified user. Also, this error may occur if the user is not local or if the email address is invalid.