Exchange 2k and AOL problems

[neaxtester2000]

Hi, all mail that we send from our company is blocked by AOL. I am working to fix this problem but am having a tough time. Hoping someone has had this same issue and can provide some insight. At this point I feel the problem is because when performing a reverse DNS lookup of our IP, it fails. This is why I think we cannot send mail to AOL users. Our system is setup like this. I am going to use fake info but hopefully you can understand:

Domain: test.com
mail.test.com = x.x.x.30

x.x.x.30 is nat'd to an internal ip that is our spam filter. its then forwarded to our exchange server.
now the exchange server is nat'd to x.x.x.2
I am not too familiar with all of this so my terms maybe used incorrectly and I apologize ahead of time for that. I can provide any additional info that is needed, Thanks

 

[tony72000]

You are on the right track regarding your reverse DNS. As your sending IP address can not be resolved, the emails are getting rejected.

Can you use a smart host? (send your emails through your ISP, as there servers IP will have a reverse DNS)

 

[bobsa32]

Some ISP's require that your mail is forwarded through a smart host rather than sent using DNS. As far as i am aware AOL are one of these ISP's.

Contact your internet provider and ask what their smart host is EX. smtp.copperstream.co.uk

this should resolve your problem

 

[58sniper]

This isn't likely a smarthost issue, since they're attempting to send TO AOL, not FROM AOL. The RFC says that you MUST have a reverse DNS entry for the public IP address used by your sending server (the same RFC also says that you cannot block mail if there is no reverse DNS entry, but AOL doesn't play by the rules).

While a smarthost might resolve the problem, it's only because the smarthost would have a reverse DNS entry. Using a smarthost also has negative implications with delivery receipts.

Best bet - run your IP address through the reverse DNS check at

http://dnsstuff.com/

and see if there's an error. If there is, talk to your ISP (who owns the IP address), and ask them to create and rdns (PTR record) for you.

Pat Richard, MCSE MCSA:Messaging CNA
Want to know how email works? Read for yourself -

http://www.ietf.org/rfc/rfc2821.txt