Question : Windows 2003 SMTP failed to receive external emails. SMTP's fault or DNS fault?

Dear experts:

My hosting company provides me with a VPS on Windows 2003 and a static IP.  I connect to it through XP remote desktop and build my own web site.  Set up and configuration go smoothly with the Web server and FTP servers through port 80 and port 21.  But receiving problem exists after putting up the SMTP server.  After the SMTP is set up, I see that in IIS manager, the server has 2 domain names: the computer name as Local (default); and the web site domain name as Local (custom).  In pop3 server manager, I have the web site domain name under the computer name with the mail boxes I created.  I also create accounts in outlook express with names similar to the mail box. Then I telnet port 25, below is the result.

telnet mail.webDomainName.com 25
220 computerName Microsoft ESMTP MAIL Service, Version: 6.0.3790.3959 ready a
t  Sun, 15 Nov 2009 04:26:00 +0800
helo mail.webDomainName.com
250 computerName Hello [58.164.132.185]
mail from:admin@webDomainName.com
250 2.1.0 admin@webDomainName.com....Sender OK
rcpt to:user@telus.net
250 2.1.5 user@telus.net
data
354 Start mail input; end with .
subject: Test Message
This is a telnet test.
.
250 2.6.0 computerName> Queued mail for delivery
quit
221 2.0.0 computerName Service closing transmission channel
Connection to host lost.

The telnet message looks good and the email delivered successfully (I tested 4 email accounts, all were successful)

I then sent emails from the 4 emails account.  All were bounced.  I tried sending from one account I created in the VPS to another; this internal emails were received successfully.  At this point, I think the next bet is MX record; so I put up the DNS server, make it a primary zone, and create A, MX and PTR records.  Below is the nslookup test for the server and the MX record:

C:\Documents and Settings\Administrator>nslookup 58.164.132.185 127.0.0.1
Server:  localhost
Address:  127.0.0.1

Name:    www.webDomainName.com
Address:  58.164.132.185


C:\Documents and Settings\Administrator>nslookup
Default Server:  dns11.nwtgigalink.com
Address:  203.98.160.11

> server 58.164.132.185
Default Server:  [58.164.132.185]
Address:  58.164.132.185

> set q=mx
> webDomainName.com
Server:  [58.164.132.185]
Address:  58.164.132.185

webDomainName.com  MX preference = 10, mail exchanger = mail.webDomain.com

The default server dns11.nwtgigalink.com is given by the hosting company. I added the servers IP to the DNS tab of TCP/IP property.  What's more: email send from telnet has "admin@webDomainName.com" as sender; but email from Outlook Express has "admin" as sender. Can anyone tell me what is the reason this server failed to receive external email and how may I correct that?

Thank you!

Answer : Windows 2003 SMTP failed to receive external emails. SMTP's fault or DNS fault?

easiest would be if you post the real domain than we can check.
But: If telnet is NOT working, than your problem if most likely your firewall, than is not correctly forwarding connection to Port 25 to your internal Mailserver Port 25 !