Comments on: Trouble shoot domain name issue using nslookup

By: admin

admin — Fri, 10 Jul 2009 09:38:24 +0000

The easiest way – use network port scanner software – a lot are available on the internet ^^

The error message shows that the email server has implemented policy such that it will not allow other people to use it as an email relay server – a waste of resource from their organization view of point.

By: ojchong

ojchong — Fri, 10 Jul 2009 03:30:34 +0000

I found out that some email server able to connect by telnet to port 25 and 587. How do we determine which port they using?

Thanks for your help. I got it.

220 sgperak.mschosting.com
helo xxxxxxxxx
250 sgperak.mschosting.com Hello [115.132.2.248]
mail from:xxx@domain.com
250 OK Sender ok
rcpt to:xxxxxxx@domain.com
550 Authentication is required for relay
rcpt to:xxx@domain.com
250 OK Recipient ok

*550 Authentication is required for relay [what possible this error message could be?]

haha. Still remember me huh? (happy) YES, in network industry now.

By: admin

admin — Thu, 09 Jul 2009 11:08:16 +0000

same, result are the same whether it is set type=MX and set q=MX.

You may telnet to port 25 of the email server. Some server will check the email address for the recipient to see if it is exist or not like the following:
—
c:\telnet mx.domain.com 25
…
RCPT TO:
450 Service unavailable
RCPT TO:
250 Ok
quit
221 Closing connection. Good bye.
—

In this case, apparently user2 is exist, however, user1 is not.

Hope help Joon Chong. Are you in network industry now?

By: ojchong

ojchong — Thu, 09 Jul 2009 02:21:34 +0000

interesting! set type=MX and set q=MX; is it the same? Can we check whether that email address exist or not? by using telnet?