Emails not sending with Exchange 2003 SBS

I have a weird problem here. I have Exchange running on an SBS 2003 box. For some reason it won't send mail. it just sits in the queue for ages. I can't work out why the mail won't go. if I right click and select force connection nothing happens. There appears to be no errors in the logs even when I set logging on the exchange transport to maximum. It just sits there doing not a great deal. I pretty confused to be honest. I'm sorry I can't give any detailed errors, but there don't appear to be any! Can anyone help?

Cheers

Tanjuakio
tanjuakioAsked:
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lollygagrConnect With a Mentor Commented:
Do you have RDNS/PTR records set up for the external ip of your Exchange server?  Most email servers will try to look up the connecting ip in DNS, and if there are no corresponding records, they will treat your mail as spam and either block or defer delivery.  Here is a good overview article with instructions:  http://www.amset.info/exchange/dnsconfig.asp.

If DNS is set up as above, another possible issue is the DNS being used by your SBS servers.  What are they using for primary and secondary resolution, and are there forwarders set up?  I assume you can browse to the internet from these servers ...
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tanjuakioAuthor Commented:
Quick update, I've changed the delivery method to use a smart host (mailhost.zen.co.uk) this seems to have speeded things up. I'm still confused as to why though. I have a few servers setup with different customers all using SBS 2003 and the same ISP.
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tanjuakioAuthor Commented:
I don't know if an RDNS record is set for the sending IP. beings as the mx record would point to the customers email hoster and not the exchange server I'm guessing this wouldn't help? (Incoming email is handled by POP3). That would answer the question of why email started to flow when I set a smart host I guess.
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lollygagrCommented:
MX is the DNS record used for mail delivery, but a lot of sites have started looking for RDNS to try and cut down on the spam being delivered to them.  The reasoning is that zombied spambots and fly-by-nighters won't have RDNS set up ... it's a bit heavy-handed but fairly effective.  More and more sites have gone to using RDNS as one of their anti-spam tools, especially the big providers like AOL and Hotmail.   The fact that the mail started delivering when you switched to a smart host is a strong indicator that RDNS was the main issue.
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tanjuakioAuthor Commented:
their email has been runnign ok for the past week or so (having said that I'll get a call now!) So I think it was due to RDNS. Not sure what to do with the points though.
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