[Host Unreachable] Exchange 5.5 Internet mail service 5

[gp8]

Hi , 99% of mails leave the IMS OK but a few will just sit and when looking at the details it says [Host unreachable]. I have tried nslookup to the host and get a valid response, I have even managed to ping the host in some instances
I have tried different dns servers address's with no result.
I have set the dns cache on the exchange server to force a dns resolution every time it sends a mail.
Any Ideas anyone???

Ged

 

[fletchy]

I have had this issue for a few weeks now and it got to be a real issue at my company. As most of you have done above i checked the SMTP logs and the event logs, without much success.

eventually i noticed that the messages getting stuck were from just one of our 2 mailbox servers, after investigating i found that the IP address of the email server had been previousley used by another system, quite some time ago. although all reminents had been removed from DNS an entry still existed in WINS, all our servers had "Use Wins for DNS resolution" enabled. Once i deleted the rogue entries emails were delivered ok, You will have to delete ones currently stuck on the queue as they will have the wrong server appended to the message id (if your problem is the same as mine was).

Even so i would say that anyone with this should concentrate on name resolution as teh most likely cause

I hope this helps some of you

 

[Goher]

I have been having a similar problem but recently discovered I had old WINS entries....after amending these it resolved the prob...cheers for your help fletchy

 

[pdurkee]

I have seen this problem and I have a similiar setup. My ISP/telecom provider did not have a reverse dns entry setup on my account. The site I was sending email to would reject any email that did not have a reverse DNS, (possible spam). I added this and the company mail server that was giving the error would receive my mail. You can got to dnsstuff.com and check for reverse dns. There was a lot of different info in this thread, but this may help.

pdurkee

 

[rascrasc]

Are you running Trend Micro ScanMail 3.82?


We also have this problem since switching from NAI Groupshield to Trend Micro ScanMail v3.82...
Because we never experienced this problem the past 6 years (running NAI) - I had a look to the Trend-Micro support web site...

Look for Hotfix 1128 and 1160.
Trend Micro solutionID: 20113

http://de.trendmicro-europe.com/enterprise/support/knowledge_base_detail.php?solutionId=20113

 

[Woosie]

I have also had the same issues since installing Scanmail v 3.82 (having upgraded from 3.5)

3.82 seems to include a seperate configuration for scanning of inbound/outbound IMS messages. When enabled, all messages stick in the outbound queue with host unreachable even though I am not using DNS to send messages, instead all messages are forwarded to a mailrelay. I have tested communication with it on port 25 and it works fine hence this makes no sense at all.

Having tried a few things, to fix the issue, I finally disabled IMS scanning on the scanmail v 3.82 configuration screen and all messages now flow through fine. As it is configured to send to a relay, messages are scanned there for virus acitivity hence disabling this option on the IMS server is not an issue...

 

[royalraven]

Just putting in my two cents as I came across this similar issue and ultimately found my solution within the same day. My issue was caused by McAfee VirusScan 8.0i (which has built-in firewall capabilties) blocking port 25. After reconfiguring the policy to exclude this port, everything went through fine. A simple solution to a complex issue - it took me a while to come to this conclusion after investigating and pursuing all of the other information in this post.

Hope this helps someone else....

 

[snowone]

We are having a similar issue here, on MS Exchange 5.5 / winnt4.0

Messages generate the following error immediately when sent...

>>>Error<<<
Your message did not reach some or all of the intended recipients.

Subject: RE: Email test
Sent: 1/25/2005 11:32 AM

The following recipient(s) could not be reached:

'Recipient@isp.net' on 1/25/2005 11:32 AM
The recipient name is not recognized
The MTS-ID of the original message is: c=US;a= ;p=ESG;l=SERVER-050125193138Z-173
>>End Error<<

- Issue is isolated to domains at ONE ISP, using same host
- Confirmed successful ping and communication from our Exchange server to IP and host name of remote mail server
- Had our domain Whitelisted, despite no RBL entry found for our domain.
- Confirmed we have reverse DNS entries correct
- Mail can be sent from gmail to same remote email addresses
- We have no local spam filter, and AV was confirmed to not be blocking.
- Firewall SMTP proxy set to allow any to any outbound.

*contacted both ISP's and recieved no insight/resolution.

Any one have ideas on where to look next? This seems to have started mid-December.