If you find that some of your outbound emails bounce back to your inbox with a "550 Relay Denied" or similar "relay" error message, it's likely due to your ISP (Internet Service Provider) detecting an attempt to send out email that is not routed through their email server.
Many ISPs, in an effort to reduce the amount of spam that is sent through their network, mandate that you route all outbound mail through the ISP's server. By requiring that all outgoing mail be sent through their SMTP (outgoing mail) server, your ISP is able to monitor data that gets sent through their network and uses their resources.
For more information, see this Microsoft reference page.
The "relay" errors generally only occur when using an email client program such as MS Outlook. Using a normal web browser to access your Volusion webmail and send messages should not cause these errors.
To correct this issue and ensure that you do not continue to receive errors when sending out email, you need to change the SMTP (outgoing mail) server settings in your email client program to match the outgoing mail server of your ISP. For specific instructions on how to use your local ISP for outbound mail, you should visit your ISP's informational pages or contact their customer support team.
You should continue to use the Volusion inbound (POP3) email server to retrieve your incoming mail.