The server you connected to requires you to log in (SMTP AUTH) or to start TLS before sending.
Policy rejection · fixable
Common causes
- Mail client or website plugin not set to authenticate
- Using port 25 instead of 587 for submission
- STARTTLS not enabled
How to fix it
- Use port 587 with STARTTLS (or 465 with SSL) and enter the mailbox username and password
- Enable "My server requires authentication" in your mail client
- For WordPress, configure an SMTP plugin with your provider's settings
SMTP TesterRun the right check for your domain or paste the full bounce message for a precise explanation.
Open SMTP Tester →Frequently asked questions
Which port should my website use to send email?
Port 587 with STARTTLS and a login is the standard for submitting mail.