The error 5.7.1 is an SMTP error that occurs in the Thunderbird email client when authentication is required to send emails for better protection. The error occurs, followed by the message as relaying denied. If you receive the relaying prohibited error, it means that the outgoing mail server couldn’t authenticate you as a legitimate user. You may receive the error when you are trying to send an email message to a recipient outside of your domain. Let’s see how to fix Thunderbird email error 5.7.1 using the steps that are given below.
To change the email address, open the Email application.
Emails that you have deleted will be in the trash..
To archive the emails first, sign into the Gmail account.
First, log into the account and extend the side tab..