exchange connecting to wrong email server

Microsoft Exchange 2003
i setup a microsoft small business server 2003 using network solutions for dns hosting. i enabled smtp logging because of this problem, incoming email to our domain has no problems. i could also email tons of other domains no problem as well. it seems like when my domain emails a domain that uses appriver or mxlogic as their spam provider emails intermittently bounce. i found a pattern of the problem in my smtp log. anytime our server connects to their website IP (which it shouldn't in the first place right?) email bounces back with User Unknown or Relaying Denied non delivery reports. (of course it will bounce back because the user probably doesn't exist or that mail server could be running but not accepting mail.) why would it connect to their website IP and not their MX record IP? my exchange server looks up another domains email server by mx records right? it can't get it wrong can it? if it connects to their spam provider first then mail gets delivered ok. the IP of domains that i get the bounced mail from i could telnet into port 25 and it responds back as a mail server of some sort... it could be their old server but why would our exchange server connect to their old website/mail server instead of their new mail server/MX record? is this a problem with my mail server or do they have outdated dns or mx records somewhere?

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We have just seen a similar issue in the field. It is a real simple fix. You need to call your ISP or if you manage your own DNS you need to set a reverse lookup for your mail server.

Some ISPs will just deny your emails if your reverse IP does not in fact point to your sending mail server.

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  • Sarje
    Try to use network sniffer, best one is Ethersnoop by Archisoft. Then filter by smtp. It will show you how the packet goes. If the message is rejected then observe by this sniffer you will get the solution. also this method is also useful to track network problems
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  • HCream
    I don't think it's the Reverse IP Lookup problem as described by JohnyAdmin. Because Dv8ed736 pointed out that emails DO get through if connected to the recipient's email filter service server. Dv8ed736's suspicion is right that the recipeent's MX Records are in question. They may have an old mail server record left in there, or the record order is not properly arranged. You should contact their email administrator to point out the problem you've experienced. It's possible they can't fix the problem themselves. If your SMTP server has an outgoing IP address filter function, you can add that IP address to the block list. Hopefully your server will locate the other GOOD addresses to make a connection.
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