I setup fedora core 6 with an email server(sendmail) to replace my old email server.My new email server working fine when i setup my local IP of my new server same as my old email server IP(let say is 192.168.1.1).But when i try to change the IP address of new email server to other IP it does not work at all.I dont know where is the problem but i do suspect is the problem with my DNS server which is on other machine.i did try to configure my dns server to point my new email server IP but it does not works as well.any idea???

No, the problem probably lies in your router or firewall if the address of the machine locally is 192.168.1.1. Your router is forwarding traffic from port 25 (SMTP) on its public address to port 25 on 192.168.1.1. If you move the server to 192.168.1.99, and the firewall/router is still trying to forward it to 192.168.1.1, that would cause the problem. Make sure if the server has a private IP address that the router/firewall is sending to the correct address.

It would only be a DNS problem if the mail server had a real IP address, IE one that can directly reached from the internet. If it was moved from say 99.98.97.96 to 99.98.97.100, then the DNS would also have to be changed.

Peace,
JimBass

Thanks for your help.I already forward my port 25 and 110 on the new IP i configure.I still can not get it work.Is that possible problem with my MX records???

If you have port forwarding correct, then the problem could be with MX records. It also could be some other things.

Is your connection to the internet a cable modem or home DSL, where you have not purchased a static IP? I know often you'll keep the same address for months/years, but it can also change. I would do something like this to check on this possibility . By name_of_your_mail_server, I mean whatever name the MX points to.

Then check what IP you are trying to ping, say 1.2.3.4 for example. Then, on a browser, go to http://ipchicken.com and see what your address is. If IP chicken says the same address that the ping tried to reach, you're ok. It doesn't matter if the ping succeeds or fails, just that they agree on the IP address. If you're using a dynamic address service, like noip.com or dyndns.org than this problem would be avoided.

It would also help us to help you if you published what your domain name is, but that is your choice.

Peace,
JimBass

Thanks for quick response.I do have static IP and domain name.My task is to change the old email server to this new server.Im new to sendmail or to setup an email server.I just want to find out what is the problem that i cant use other IP address other then the old email server IP.my new email server just work fine under if under old email server IP address.

Well, if you do have a static address or addresses, do the test I suggested. Move the server to the new address. Tell your mail server to ping itself by name, mail.domain.com, or smtp.domain.com or whatever your MX is. Then goto http://ipchicken.com and see if the answer you get from that is the same as the address you tried to ping. If it is the same, then you have a problem with port forwarding. If they are different addresses, then you just need to update the DNS to show the new IP address for your mail server.

Peace,
JimBass

Thanks.i configure 2 MX record for my email server.
smtp.mydomain.com [0]---->old server
server.mydomain.com [5]---->new server

when i try to ping server.mydomain.com

PING server.mydomain.com (1.2.3.4) 56(84) bytes of data.
64 bytes from smtp.mydomain.com (1.2.3.4): icmp_seq=1 ttl=63 time=0.558 ms
64 bytes from smtp.mydomain.com (1.2.3.4): icmp_seq=2 ttl=63 time=0.455 ms

i get the above result.my ip is same as in ipchicken.com.but the problem is i get the response from "smtp.mydomain.com" but not "server.mydomain.com".that make me confuse.anyway i oso need some help on configure DNS to point to my email server.

The reason you see responses from smtp.mydomain.com when you ping server.mydomain.com is because there is a PTR record that has smtp.mydomain.com associated with your public IP address. That is the correct way for a mail server to be configured. What is happening here is when you try to ping server.mydomain.com, the DNS responds with the IP address 1.2.3.4. You try to ping 1.2.3.4, and your lookup also checks the reverse map (PTR), and finds that your public address has a PTR for 1.2.3.4, and that PTR is smtp.mydomain.com, so the ping replies that it is getting returns from smtp.mydomain.com, because that is how your public address is identified. I bet very much you could disconnect smtp.mydomain.com from the network, and you'd still see replies being listed as smtp.mydomain.com.

This also assumes you only have one public address?

I still suspect that you are not correctly mapping ports 25 and 110 to the new server. As you have not told us what your domain name is, that is the best guess I can make without having anything concrete to look at. It is also possible that something on the mail server isn't functioning properly, but since we don't know the domain in question, there is no investigation we can do to find out if that is the case.

All you have to do on the DNS is remove the smtp.domain.com subdomain and its MX, and everything should go to the new server, if you correct the problems with it. You'd also need to get a new PTR, though by far it would be easier to put the new server in place of the old one, with the same public and private address.

Again, the choice to tell us your true domain name is yours. If you choose not to tell us that's fine, but there is nothing else I am able or willing to do in a theoretical sense.

Peace,
JimBass