SMTP Authentication at Site5
For added security and spam protection, we’ve ensured that pop-before-smtp connections are disabled on our servers. What this means is that every outbound mail connection (SMTP connection) must be authenticated and can not just be sent without logging in.
Of course, having this added layer of security does produce errors when connections are not made properly. If your email is being sent using a connection that has not been authenticated, you may see an error such as this:
[18.104.22.1689]:49593 is not permitted to relay through this server without authentication.. Please check the message recipient email@example.com and try again.
If you do run into a problem such as this, the solution would be to ensure SMTP Authentication is enabled within your email app or script. If you have difficulties configuring SMTP authentication within your email client, please feel free to reach out to our support staff!
Once SMTP authentication has been enabled in your mail client, you should see no further problems sending mail!