Error 503 Valid RCPT command must precede DATA can occur when sending an email. It’s telling you that your email server did not properly authenticate your SMTP (outgoing mail) connection.
The two most common causes for this error are:
- Your email server requires you to check email first before sending an email (checking email first is one way your email provider manages the security of your email account).
- Your email client isn’t set up for SMTP Authentication.
The steps to fix this error vary based on the email service provider you’re using. Choose from the following Knowledge Base articles to solve the error on your email.
If you need help with your HostPapa account, please open a support ticket from your dashboard.