ZCS ROCKS! Need some DNS help!

[SiteDiscovery]

I seem to be having some weird DNS issues with the server. I do not have the ZCS server running as a dns server - only as a client. All requests are sent out to my main DNS server. Somehow, it has it in the cache somewhere that sbcglobal.net is at sbcglobal.net.mydomain.com.. I cannot seem to clear this entry wherever it may be at. I have changed the DNS server to 3 different servers and I get the same response. If I ping that name from another server, it resolves fine on the same DNS servers. So I can conclude that the ZCS server is resolving locally for this site and looking at the DNS servers for the others. Weird..So.. How do I clear the local DNS cache on a Zimbra server? Is there a local DNS cache that could be corrupted on the ZCS server?

A LOT of my outgoing mail is being deferred. The common error is connection timed out. Can this be related to a DNS issue? I have sent mail to the major providers (AOL,MSN,YAHOO) and about 60% of them time out. I have checked DNS resolution from the terminal and I am resolving the names and MX servers correctly. Do I need to enable some DNS checking on the server? What could be causing these messages to time out?

When I check the deferred window, all my mail seems to be coming from localhost.localdomain. I have the host file set correctly as per the instructions. (127.0.0.1 localhost / 192.168.1.203 zcs zcs."mydomain".com - replace "my domain" with my actual domain). Is this normal or should it say that mail orginates from zcs."my domain".com?

I'll post any log that needs to be seen. Just tell me what to post. I'm kinda a newbie at this mail stuff.

Thanks a million!

Confused??? So am I?

[phoenix]

Is your /etc/hosts file correct? Details of that are covered in the Zimbra quick start guide and several threads in the forums or post the details if you like. Where is your DNS hosted? Is it externally or internal? Are you behind a firewall? If so you probably need a split-DNS set-up like this example. You'll need a local DNS server if you're using split-DNS.

[SiteDiscovery]

The /et/hosts file has the correct entries in it. I can ping and telnet to the mail server from itself using the external IP so I assume that Postfix is not having an issue with my Firewall.

I have set up a split DNS per the wiki instructions. I still cannot resolve any address going to sbcglobal.net. When I ping the domain, it resolves to sbcglobal.net.mydomain.com. (66.166.18.139). This is my external IP address. When I do a nslookup and set the type=mx, I find the mail servers just fine. The error in the deferred que is "connection refused" and it shows my external IP address as the resovled address for sbcglobal.net. Any ideas? Why is only one domain not being forwarded and resolved locally? sbcglobal.net.mydomain.com..? (the extra period is not a typo). Where does Zimbra hold cached DNS entries? I assume that the cache is corrupted since it is not even trying to use the external DNS only on this entry.

Why does all my mail in the mail queues seem to come from localhost.localdomain when I have the appropriate entry in the /etc/hosts file? Is this normal?
Will the split DNS take care of this issue?

Let me know your thoughts..

Thanks!!

[phoenix]

Of course you can ping and telnet to the server using the IP, that's not the problem but DNS resolution is. Post the details of your /etc/hosts file I can't answer about sbcglobal.net.mydomain.com as I don't know what the address/domain name is that you're trying to send it to. Have you done any 'dig' commands to see if your domain name & A/MX records resolve correctly?

Is this PC connected directly to the internet or behind a firewall (apart from the one on the server)? Which O/S is this on? Is this a NE or OSS Zimbra server? Have you disabled any SELinux (if that's on your system)?

[SiteDiscovery]

Originally Posted by phoenix

Of course you can ping and telnet to the server using the IP, that's not the problem but DNS resolution is. Post the details of your /etc/hosts file I can't answer about sbcglobal.net.mydomain.com as I don't know what the address/domain name is that you're trying to send it to. Have you done any 'dig' commands to see if your domain name & A/MX records resolve correctly?

Is this PC connected directly to the internet or behind a firewall (apart from the one on the server)? Which O/S is this on? Is this a NE or OSS Zimbra server? Have you disabled any SELinux (if that's on your system)?

This is behind a firewall. I have the appropriate ports forwarded.
SELinux and Firewall have been turned off.
I am running this on CentOS 4
Specs:
P4 3.2Ghz
512MB Ram
Dual SATA HDD
RAID 1
Single NIC

I cannot ping SBCGLOBAL.NET on my outside system at all. It comes up as:
ping: cannot resolve sbcglobal.net: Unknown host.

On my zcs server, it comes up as:
[root@zcs etc]# ping sbcglobal.net
PING sbcglobal.net.sitediscovery.com (75.31.55.210) 56(84) bytes of data.
64 bytes from adsl-75-31-55-210.dsl.scrm01.sbcglobal.net (75.31.55.210): icmp_seq=0 ttl=64 time=0.313 ms

Why is my zcs server resolving the entire sbcglobal.net domain to my external ip?


****HOSTS FILE****
# Do not remove the following line, or various programs
# that require network functionality will fail.
127.0.0.1 localhost.localdomain localhost
192.168.4.20 zcs.sitediscovery.com zcs



****DIG RESULTS ON SITEDISCOVERY.COM****
; <<>> DiG 9.2.4 <<>> sitediscovery.com
;; global options: printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 36636
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 2, ADDITIONAL: 2

;; QUESTION SECTION:
;sitediscovery.com. IN A

;; ANSWER SECTION:
sitediscovery.com. 7200 IN A 75.31.55.210

;; AUTHORITY SECTION:
sitediscovery.com. 6402 IN NS NS49.WORLDNIC.com.
sitediscovery.com. 6402 IN NS NS50.WORLDNIC.com.

;; ADDITIONAL SECTION:
NS49.WORLDNIC.com. 142208 IN A 205.178.190.25
NS50.WORLDNIC.com. 164866 IN A 205.178.189.25

;; Query time: 126 msec
;; SERVER: 192.168.4.20#53(192.168.4.20)
;; WHEN: Sat Dec 30 09:05:01 2006
;; MSG SIZE rcvd: 130



Any ideas?
I really appreicate the help. Thank you!!!

[SiteDiscovery]

Ok.. this is weird. I was curious, so I ping'd wswig.net.

External machine:
MACBOOKPRO:~ icepick94$ ping wsywig.net
ping: cannot resolve wsywig.net: Unknown host


On the ZCS server:
[root@zcs etc]# ping wsywig.net
PING wsywig.net.sitediscovery.com (75.31.55.210) 56(84) bytes of data.

It seems that for some reason, when the server cannot resolve a host, it automatically appends my host domain to the name. Since it is doing this, it will never find the MX record for any domain that does not have a host associated with it. It can find www.sbcglobal.net just fine. It cannot resolve sbdglobal.net to get the MX record since the zcs server is adding my hostname to it. WEIRD!!

Does this help or add to the confusion?

[phoenix]

OK, as you've already said the hosts file is correct.

I'm not sure which domain you want to host your zimbra server on, is it sitediscovery.com? If that's where you want mail sent to then you don't have any MX records pointing to your server, are you able to make changes on that DNS server that hosts your records?

I also don't understand where sbcglobal.net comes into this, isn't it your ISP?

[SiteDiscovery]

Thanks for working with me..

I already have the MX records setup and have been recieving and sending mail on this server. I have found in the Deferred mail que that I have a bunch of messages backed up that either have "connection timed out" or "connection refused" as the reason why they are deferred. Now, when I investigated the connection refused issue, most of the messages that were refused were going to sbcglobal.net e-mail addresses. Here is the actual error message when I check the deferred que:

Sender:ccottingham@sitediscovery.com
From Host: localhost.localdomain
From Domain: sitediscovery.com
From IP:127.0.0.1
Reciepients:douglassw@sbcglobal.net
To Domain:sbcglobal.net
Content Filter:undefined
Size:3299243
Reason: Connect to sbcglobal.net[75.31.55.210]:connection refused.


Ok.. sbcglobal.net is not at 75.31.55.210. That is my external IP.
When I try to ping sbcglobal.net from the terminal, it gives me this:
[root@zcs ~]# ping sbcglobal.net
PING sbcglobal.net.sitediscovery.com (75.31.55.210) 56(84) bytes of data.
64 bytes from adsl-75-31-55-210.dsl.scrm01.sbcglobal.net (75.31.55.210): icmp_seq=0 ttl=64 time=0.238 ms
64 bytes from adsl-75-31-55-210.dsl.scrm01.sbcglobal.net (75.31.55.210): icmp_seq=1 ttl=64 time=0.196 ms

So, it looks like that the zcs server is taking it upon itself to append sitediscovery.com to any address that it cannot resolve. I tried this with a bogus address that does not exist and I get the same result. The zcs server appended sitediscovery.com to the name instead of reporting it as an unknown host.

Hopefully this is a bit more clear on the issue I am having. In a nutshell, I cannot send mail to any host @sbcglobal.net. I am also having issues sending mail to anyone.. I keep getting intermittant connection timed out issues. The mail just sits in the deferred que. If I requeue it, it just comes right back to the deferred que with the reason listed as either "connection timed out" or 'connection refused" .. Its driving me quite mad!!


Thanks again..

[phoenix]

I see that your MX records are set-up correctly, when I posted before I checked and didn't get any detailed MX records for your domain.

The From Host/Domain?IP are perfectly normal and what you would see on a normal email. Have you set-up the split DNS yet? I believe these problems should go away when you do that. The usual reason you get these problems of mail in the deferred queue is becasue (for some reason) there's a temporary or permanent problem with DNS. I'd suggest trying the info in the wiki and we'll revisit this when you've set-up a local DNS server.

[SiteDiscovery]

I have the DNS issues taken care of. I found that I did not have a line in the resolv.conf that I needed.
search zcs.sitediscovery.com

Once I added that, I stopped resolving unknown hosts to my external IP.
I still setup split DNS since it sounded like a good idea.

I'm going to open another thread on the mail sending issues.

Thanks!!