Error: SMTP Error 511

What's Causing This Error

SMTP error 511 is a duplicate of SMTP error 510. SMTP error 511 occurs when the recipient's email address is incorrect or invalid; therefore, the email server rejects the email address.

Solution - Here's How To Resolve It

A simple fix for this error is to validate the recipient's email address and verify if there is a valid email account on the recipient's email server. Also, it is essential to check the validity of all recipients if there are multiple email addresses.