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message non delivery Exch 5.5

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by rcoolman

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A certain e-mail server is refusing mail from our company's Exch 5.5 server with the following message. Anybody know how to fix this? Thanks!

553 Your computer does not have a hostname, access blocked

5 replies

by jguasch

I believe that is a blocking rule on the target email server. Sometimes domains are black listed (spam). You need to inform the Exchange administrator from the otherside to remove you from the list.

by rcoolman

Yes, I'm sure the recipient server has something to do with it, but not a blacklist - it is requiring something my server isn't doing. I need to know how to comply if that's possible. I'm sure they aren't going to change their policies to accommodate us.

by jguasch

Usually, open relay is the thing that gets you blocked. Check your firewall and mail server for open relay.

by jguasch

Ha! ok gave you the wrong info since it is not a block list thing.

Basically they're using reverse dns lookup for your IP and that fails. Let me look some more.

by jguasch

Ok.. you need to contact your provider and have them add the entry for your firewall and IP on dns zone files. Basically, say your server is named firewall and your domain is domain.com with IP 1.2.3.4, you need to ask them to add on dns zone files an entry for firewall.domain.com with IP 1.2.3.4.

So when the target does a reverse lookup, it will resolve to your firewall (or mail server if your mail server is out in the internet).

Hope that helps.

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