Our exchange 5.5 server is having a hard time sending to comcast.net
In the outbound queue it is stuck as host unreachable and bounces back within a few minutes.
The nslookup and restest.exe both come back looking good... however... if I telnet comcast.net 25 I do not get a responce. When I telnet on port 25 using their MX entry ip's, I get an immediate response.
It sounds like a DNS issue, but I am not sure where to start.
EDIT: I just set the dns IP to my ISP's DNS instead of my internal one. I tried the telnet comcast.net 25 and it came up with a connect failed, but the telnet with the ip address connected fine right away again. Could it be my isp's fault?
Thanks in advance, Jayson
< Message edited by SaumZ -- 9.Mar.2006 5:14:07 PM >
Hey. I had the same problem with hotmail.com and msn.com.
I contacted hotmail/msn (suprizingly, very helpful guys there!) and we tried all of the things you have done. And they confirmed that there was no blocking on their end.
They use 8 different IP addresses for load balancing with only 6 of them in use at any time (so there are always 2 "dead" ip addresses). I even tried bypassing the whole name resolution thing by putting a current "hot" IP (supplied by the MSN guys) into my HOSTS file. No joy.
What finally worked is that I changed the PRIMARY DNS server on the 5.5 box and pointed it to one of the SpeakEasy name servers. (66.93.87.2 in this case) NOTE: SpeakEasy is NOT my provider. XO.com is (and they suck, by they way).
...and ZINGO out went my OUT queue!
I would try using a couple of different KNOWN GOOD DNS SERVERS and see how it goes.
Check your Delivery Restrictions. If there is no problem there, check the CONNECTIONS tab and the Accept Connections section.
If all is good there this is what I did.
Using some other SMTP server (there are freeware ones out there) installed on another machine try sending a message. Make sure that the new SMTP server is on the same subnet and on the same side of the NAT as your 5.5 server. Make sure the appropriate ports on your WAN router are configured. If the message gets through, you definately have a problem with the Exchange box. If it doesn't get through then your problem is either name resoltion or network related. (PS: if you don't get a resoponse, be sure to try other addresses NOT on comcast.net to confirm you have your SMTP set up right)
One other thing. Do a ping sweep of the subnet your ISP has you on. Likely you will find one or two other entities. Run a WHOIS on them and give them a call. Ask what kind of email server they are running (if at all) and ask if they are having the same problems you are. If they are, you have a very strong case when you call your provider. If they aren't well, at least you got to know your IP neighbors---always good info.
You said when you telnet it just drops the connection?
Are you sure you are not blacklisted in comcast?
Try a telnet from a system outside your network and replace the mailfrom part in the below example to yorename@yourdomain.com
220 rwcrmxc24.comcast.net - Maillennium ESMTP/MULTIBOX rwcrmxc24 #338 ehlo ramee.com 250-rwcrmxc24.comcast.net 250-7BIT 250-8BITMIME 250-DSN 250-EXPN 250-HELP 250-NOOP 250-PIPELINING 250-SIZE 15728640 250-VERS V05.00c++ 250 XMVP 2 mail from: saasjask@ramee.com 521-EHLO/HELO from sender 202.81.131.64 does not map to ramee.com in DNS 521-sending machine name must be provided as a fully 521-qualified domain via EHLO/HELO command. 521-see section 4.1.1.1 and 4.1.4 of RFC 2821 521 521: Comcast requires that all mail servers must have a PTR record with a va lid Reverse DNS entry. Currently your mailserver does not fill that requirement. For more information, refer to: http://www.comcast.net/help/faq/index.jsp?faq=E mail118405
If you get prompt like what you have below possibly you may be blacklisted.
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