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.
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.
View all errors
Send up to 10,000 notifications every month, for free.
Get started for free
Send up to 10,000 notifications every month, for free.
Get started for free
© 2024 Courier. All rights reserved.