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the 203 IP is NOT hotmail so I'm assuming it is yours or your ISPs.
I believe the message is telling you that they refused to accept the email from the 203 IP because there is no reverse lookup for it so they can't verify who it is. Many people do a reverse (PTR) lookup for IPs attempting to send email to them to prevent spam.
When I attempted a lookup on the 203 IP it came back servfail meaning there is no PTR record for it or the DNS server that serves it is down. (Most likely the former.)
When I did a whois for the IP it came up showing in part:
inetnum: 188.8.131.52 - 184.108.40.206
descr: Smart Broadband Incorporated
descr: Wireless Broadband Access
descr: Ayala Avenue, Makati City
That inetnum line indicates to me that Smart Broadband Incorporated is saying they own the entire range described. You may wish to run whois on the IP yourself for further information. If they've delegated the IP to you then you may need to make your own PTR record in DNS and if they haven't you'll need to ask them to create one in their DNS server.
The actual scenario is this, I have mail server which is built in slackware 10.2 then with two IP address which is the internal IP which is part of internal domain and one public IP, My second server which is my ISA server and internet server, which is the smart bro.
By the way My mail server has its own internet provider. it is separated by internal domain.
I can't figure out the conflict of my structures. Before I use ms exchange as my mail but because its to expensive buying cals we decided to changes it into linux, I did not change my firewall only the mail. and in able for us to make mails outside our domain we use squirrelmail as our mail.
OK - there needs to be a reverse lookup (PTR) created in DNS that resolves this IP to a name. If you are hosting DNS yourself AND they have delegated the range to you then you need to add the PTR. If they have NOT delegated the range to you then you need to have Smart add the PTR.
Note that just because they assign an IP or IP range to you does NOT mean they delegate it to you in DNS. Typically you have to ask for the DNS delegation to be done if you want to host DNS PTR records for the assigned IP or IP range.