Question : Diagnostic-Code: smtp;550 Requested action not taken: mailbox unavailable

Hi there:

I am having a problem with exchange, I just change the ISP to Comcast and  I am able to send emails but when I want to send back an email from outside email accoutn (ex: hotmail), the email bounced with this error.

Reporting-MTA: dns;blu139-omc3-s17.blu139.hotmail.com
Received-From-MTA: dns;BLU131-W18
Arrival-Date: Tue, 26 Feb 2008 17:38:38 -0800

Final-Recipient: rfc822;[email protected]m
Action: failed
Status: 5.5.0
Diagnostic-Code: smtp;550 Requested action not taken: mailbox unavailable

I telnet the website and is working in port 25, also pop3 110 is working

can you help me with this?

Answer : Diagnostic-Code: smtp;550 Requested action not taken: mailbox unavailable

I figured out, I open port 587 on smtp service and it is working