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Not receiving external emails

By quintar51 ·
Background info:
I have a windows 2000 Active Directory Domain with service pack 3. I have one DC/DNS/EXCHANGE server. I'm running Exchange 2000 with service pack 3. I have a router with port 25 enabled for SMTP traffic. The same port is specified in Exchange as well.

Problem:

I am unable to receive External email ONLY. Also, I can send to hosts outside my network, but I can't send INTO my network. I don't get any errors or anything saying that the message is undeliverable.

I'm not sure if DNS is the issue here, but I do have an MX record pointing to my email server, which is the 2000 server itself.

Also, one important point. This exact setup did work in the past. I since rebuilt my server, but the setup is exactly the same.

Does anyone have any suggestions?

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Not receiving external emails

by quintar51 In reply to Not receiving external em ...

An update regarding my troubleshooting so far.

I have an internet email account which I setup on one of my clients. This account uses smtp and pop3 traffic, and i'm able to receive email there. That means SMTP is going through, so the router isnot the problem.

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Not receiving external emails

by LordInfidel In reply to Not receiving external em ...

There are several places to check here.

I normally don't accept e-mails offline. But if you send an e-mail to lordinfidel@directionweb.com
I can take a look at it externally and see where it is getting stopped.

The areas that could be stopping it is
1- firewall
2- incorrect rules on firewall
3- incorrect mx record
4- no domain specified in exch

As a point of record, you should not be running dns and exch (much less a AD DC) on the same machine.

Although I do this for small clients, running dns and AD on the DC. It is actually not the reccomended way. It has to do with if DNS get's corrupt and you reboot, and the DC can not register itself in DNS, AD will fail and it will become a contstant loop state.

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Not receiving external emails

by quintar51 In reply to Not receiving external em ...

Hi, thanks for the tip.

I try installing exchange on a different machine and see if the problem is resolved.

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Not receiving external emails

by LordInfidel In reply to Not receiving external em ...

Let's look at this logically before you go installing on a new machine.

You said that prior to the new machine you had no problems.

You built a new machine, changed the MX record and you can send but can't receive.

If nothing has changed onthe firewall, and the settings are exactly the same.

And from the outside you can telnet into the server like so telnet machineIP 25

Then the 1 place I would consider a culprit is DNS propagation.

Start up a cmd prompt, start nslookup.type in set type=ns
then att.com

select one of their name servers IP's and go
server IP
(This will change the NS that you are sitting on)

Now set type=mx
type in your DomainName only, ie mydomain.com

What are the IP's returned? Are theycorrect? If they are not correct then that is your problem. You need to see what the TTL is set for your records.

If it *is* correct. Then you need to go from the outside and try to telnet into your mailserver. If you can't then it is your firewall. Make sure that you are allowing new inbound from all above tcp 1024 to mail sever IP tcp 25

If that is there, then make sure that you have specified your domains that exchange is responsible for.

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Not receiving external emails

by quintar51 In reply to Not receiving external em ...

hmmm I do think the problem is with the DNS like you've mentioned. Okay, I went through the steps you've outlined, and when I looked up my domain, it didn't come back with an IP address. Instead it came back witH A weird answer. You can check by looking for rk-ane.com. That's my domain. I think it's something with zoneedit.com, which hosts my A and MX records. They point to my DNS server for email and WWW. I was sure I set up everything correctly there. See, if I run nslookup for my A record, it does come back with the correct IP.

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Not receiving external emails

by LordInfidel In reply to Not receiving external em ...

Found your problem. It is in DNS.

Your MX preference is set to 0, it needs to be 20.

I set it at 20 so if I have to add another sever in during a pinch, I can set it at 10.

> set type=mx
> rk-ane.com
Server: internal
Address: 192.168.0.1

rk-ane.com MX preference = 0, mail exchanger = mail.rk-ane.com
rk-ane.com nameserver = ns7.zoneedit.com
rk-ane.com nameserver = ns14.zoneedit.com
ns7.zoneedit.com internet address = 207.228.252.107
ns14.zoneedit.com internet address = 209.126.159.80
> set type=a
> mail.rk-ane.com
Server: internal
Address: 192.168.0.1

Name: mail.rk-ane.com
Address: 216.126.89.102

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Not receiving external emails

by LordInfidel In reply to Not receiving external em ...

Also,

C>telnet mail.rk-ane.com 25
Connecting To mail.rk-ane.com...Could not open a connection to host on port 25 :
Connect failed

Which means that the mail server or firewall is actively rejecting connections to tcp 25.

This needs to be opened at your firewall.

from any tcp <=1024 to mail tcp 25

I can do a port scan, but unless I am sitting on your network, it will just be a bunch of false positives.

if you were able to telnet to that port from internally, then it is not the mail server but the firewall.

So you have 2 issues going on. 1 is DNS and the second is the port being opened.

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Not receiving external emails

by quintar51 In reply to Not receiving external em ...

Hi again. Regarding DNS: Now, I do have a MX record with the name servers, zoneedit.com. I can only make it either 0 or 10, can't set it to 20. Also, on my DNS server, I need to have an MX record as well correct? Because my mail server is on another machine right? And that MX record, I can set to 20 for the preference.

BTW, I will give you the points, just keep rejecting so you can add further answers. Thanks.

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Not receiving external emails

by quintar51 In reply to Not receiving external em ...

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