[afnog] Mail Server Problem

[Mensah Agbessitse]

Hi All,

I am having a serious problem that I would like to share with the group. 
There are three sites A, B and C. B is where the hub is located and connects
to the internet. A and C are connected to B by satellite by frame relay. The
whole setup is a private network.

Site A:	Is connected to Site C through site B with frame relay link. The
connection is through the satellite. It has 64Kbps bandwidth.
	IP Network: 192.168.83.0/24

Site B:	Is the main centre where both Site A and Site C links are connected.
The router at that site runs NAT so that both site can go to the internet
with E1. By the implementation of NAT site C receives the emails and Site A
clients pop their mail from site C since they are all in the same domain.

Site C:	is where the Mail Server is. Running on Windows 2000 server a mail
program called VisNetic MailServer(powerfull email server).
	Has 128Kbps bandwidth, The administrator of this site told me that
there is no problem with his mail server. 
				IP network: 192.168.84.0/24


 The problem is that Site A clients cannot send/receive their mails from
Site C mail server sometimes. 
Hence I was at site A to check it and these are what I have observed:
1-	While they cannot received, we can browse the internet.
2-	While they cannot received from Site C, I can receive from a server
sitting on a different network.
3-	A scan for ports of the domain name from
http://www.whitedomainpages.com shows that the ports on the server are ON &
OFF. What I mean by this is that when scanned, port 110  will respond and
port 25 will not. Another scan will show that port 25 will respond and port
110 will not. Simetimes both ports will respond.

		The question is why can they send and receive email easily?
 This is the view of the diagram:

    

======================================

 Mensah Bruno Agbessitse
IT Engineer 
 
GS Telecom 
No.1 Thorburn Houses,
Barnes Road, Accra
PO  Box CT2920 Accra, Ghana.
Tel: +233-21-7010015
Fax: +233-21-7010456
Mobile: +233-24-4312978
E-mail : mensah.agbessitse at gstelecom.net 
Web: www.gstelecom.net
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