Comments for iPCNetworking Blog

Comment 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.

Comment on Trouble shoot domain name issue using nslookup 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.

Comment on Trouble shoot domain name issue using nslookup 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?

Comment on Trouble shoot domain name issue using nslookup 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?

Comment on How to encrypt Cisco Password by configuring cisco waas

configuring cisco waas — Wed, 24 Dec 2008 12:11:59 +0000

I wish Cisco could get their WAAS solution right and finally beat up on Riverbed.

Comment on Problem installing Google Talk on Vista by Fumba

Fumba — Sun, 30 Nov 2008 04:19:59 +0000

Wow!!! It worked!!! Thanks.

Comment on Static route configuration by Cisco Static Route | Internet PC Networking

Cisco Static Route | Internet PC Networking — Tue, 04 Nov 2008 11:58:26 +0000

[...] my previous post on Static route configuration, I have touched on some basic of static route configuration. In this post, I will show you more [...]

Comment on How to test if a port is open on a server or PC by Do not enable unnecessary services on your PC or server | Internet PC Networking

Mon, 27 Oct 2008 02:10:49 +0000

[...] One way to check the list of ports running on your system is to go to one of the many web sites that can run a remote scan of your system and tell you how secure the system. You may also manually test if a port is open using command prompt interface in your PC. [...]

Comment on How to find port number by Disable unnecessary network services for security « Soon Giap’s wordpress blog

Thu, 16 Oct 2008 12:09:30 +0000

[...] easily establish a telnet session to the system; it needs only the address of the system and the port or socket number of the network service running on the system. The rule of thumb for TCP and UDP ports is: Turn off [...]

Comment on How to test if a port is open on a server or PC by How to test if a port is open on a server or PC - Part II

How to test if a port is open on a server or PC - Part II — Sun, 12 Oct 2008 09:19:21 +0000

[...] How to test if a port is open on a server or PC – Part II [...]