My email reply was undeliverable.

[tulip*place]

with the message : Unknown address error 550 - Relaying denied.

I received an email from a mobile number@virginvibe.com.au and sent a reply (Reply to sender).

It was returned as undeliverable with the above message.

Am I doing something wrong?

[ten*teeny*tiny*toes]

Are you replying via your phone or computer? Not pretending to have a clue, just bumping for you.

I know something as basic as picture messaging wasn't happening on hubbies phone and it was quickly sorted with a call to the provider.

[tulip*place]

Thanks tttt for bumping.    I received the email via my pc and replied back via my pc and my reply was undeliverable.

"relaying denied."  I don't have a smart phone and only access emails with my computer.    The email was sent to my email address and I replied in outlook express as normal, but it bounced back. 

[ten*teeny*tiny*toes]

Google the error, that's what I do

550 Mail Relay Error

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.

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.