My webmail is not working

[#1]

I tried to send an email to my webmail address, but it cannot be delivered. Below is the error message.
Thanks,
Alex
The following message to <hamilton36@hamilton36.plus.com> was undeliverable.
The reason for the problem:
5.1.0 - Unknown address error 550-'#5.1.0 Address rejected hamilton36@hamilton36.plus.com'

Reporting-MTA: dns; relay.ptn-ipout01.plus.net
Final-Recipient: rfc822;hamilton36@hamilton36.plus.com
Action: failed
Status: 5.0.0 (permanent failure)
Remote-MTA: dns; [84.92.2.97]
Diagnostic-Code: smtp; 5.1.0 - Unknown address error 550-'#5.1.0 Address rejected hamilton36@hamilton36.plus.com' (delivery attempts: 0)

[#2]

Looking at your account, you don't have a mailbox of that name, that's why you're getting those error messages. If that's the address being set when you send a message from webmail, you can alter that here: https://webmail.plus.net/src/options.php?optpage=personal
Change the email address shown on that page to a valid one from your account and you shouldn't have any problems.
Not sure you want to post your email address in the public domain.

[#3]

Thanks,  Chris.