When a user receives a 550 relay not permitted error, it means they are not permitted to send an email via the server that they are attempting to send an email from. When users send an email from their Internet Service Providers (ISP) mail servers, they generally do not have to authenticate themselves. This is because their ISP are able to detect that they are a customer due to the ISP controlling the users internet connection.
As we are not an ISP, the only method we can use to detect if a user is our customer and therefore allowed to send emails from our servers, is by requiring them to authenticate themselves with their username and password. If you are our customer and are attempting to send an email from one of our servers and you receive the message 550 relay not permitted, it means you have not authenticated yourself.
Depending on the software you are using, the steps required to configure your mail software to authenticate your account with our outgoing mail server may differ. We recommend you locate the tutorial for the software you are using on our email setup tutorials page, then read through the specific tutorial for your email software and make sure your settings match the setting we provide.
Once you configure your software to authenticate with our outgoing mail servers, you will stop receiving the 550 relay not permitted error message.