Host Unreachable Error while sending emails using Microsoft Outlook on Exchange Server 5.5

Posted on 2003-03-10
Medium Priority
Last Modified: 2009-12-16
Hi i am facing a strange problem on my Exchange SERVER 5.5

All of a sudden , users in the organization while sending smtp emails to the outside world recieve a System Undelivarable error message saying, that the message cannot be sent because Host was Unreachable

but when the same user uses Outlook Express a Pop3 client to send an email to the outside world , work perfectly , the other end recepient can recieve emails

Can anyone help me on this matter , its Urgent please
Question by:d3ath
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Expert Comment

ID: 8103036
OK, but OE also uses SMTP for sending... sounds like it may be some config problem with Exchange, or maybe a comms issue - are the connections to the Exch. server ok?
LVL 24

Accepted Solution

SunBow earned 900 total points
ID: 8104409
Nope. POP3 does not send, you've invalid assumption. Check for DNS and routing differences.

Expert Comment

ID: 8105354
What Cliant are the users using to
Connect to the exchange server ??
  and is it the exchange server having problems sending to
the remote host ? or do you have a mail relay?
 It seems to me if the users can use Outlook Express
and it works the problem may be in what they are using to connect to the exchange server or the exchange server it self ..When they use Outlook Express what smtp server are they using ?  
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Author Comment

ID: 8108857
SunBow yea i checked the DNS , maybe you could help me on it a little more

in my tcp/ip properties of the exchange server, i have 3 DNS ips mentioned

let me tell you something before

my Exchange server has one Network Interface , to which i have assigned 2 IP's with 2 Gateways

1st IP is the Private Ip with its Private gateway
2nd IP is the Public IP with its Gateway

Now in the DNS Tab of TCp/IP i have mentioned 3 DNS Ips,

1st DNS ip is the IP of the DNS Server which is an Active Directory Intergrated
and the Other 2 are my ISP's DNS

now the server running exchange server has a dns server should i mention that IP there also?????

please explain more if u dont mind

Expert Comment

ID: 8110140
Try moving the ISP's DNS address to the top of the search order.

Expert Comment

ID: 8110151
You haven't mentioned it, but I assume you can ping the outside world.  What does a traceroute to your ISP's DNS server show you?

Author Comment

ID: 8126334
Well u get the Points , Coz SUnBow ur question lead me to something


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