IP address can't be resolved from domain name

  • Thread starter Thread starter Ray
  • Start date Start date
R

Ray

We normally use http://smtp.DomainName to access the mail server especially
outside company network. It worked in the past but not now. If I replace
smtp.DomainName with the internal or external IPs of the mail server, it
works perfectly. Our DNS server is located at our isp, not at our office.

In the past, there was no such problem and it seems it happens after the new
server is installed. For normal user, they are more comfortable to remember
the name rather than the ip address. I have learnt that I can put the URL in
the host file but I did not do it in the past nor this new server. Can
someone advise any possible causes and fixes.



Thanks,

Ray
 
Ray,

Open command prompt and type
nslookup

on the new prompt type
smtp.domainname

see if it resolves to the IP that you are looking for. If it does not, it
means the DNS server does not have an entry for your smtp server.

Hope this helps,
Rafael
 
Rafael,

I tried it before I raised this question. Within company lan, it cannot
resolve the IP while outside company lan, it does. Thus, the DNS server
should have the entry for my smtp server. It seems it is internal issue.

Ray
 
Ray,

Is there an IP address difference when you are on the company lan or on the
outside?
maybe when you are on company lan, the gateway cannot reach the dns (the dns
is on the isp)
or is there a new firewall in between that can be stopping dns requests?

RT
 
Rafael,

On the company lan, the server is used an internal IP address while outside
the office, a public address is used via the NAT in firewall. I believe all
the clients can reach the DNS server located at ISP as they can resolve the
names of other public websites. I am at loss why only the URL cannot be
resolved internally.

Ray
 
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