LinuxQuestions.org - Sendmail Error while sendmail mail

Hi there ,
I have configured sendmail in RedHat Linux 8.0 and I am facing problem while sendmail mail.
Problem:-
When I sendmail mail from the server to any mail server on the internet it works fine, but when I connect to Linux server from Microsoft Outlook Express I get error message as follows

"The message could not be sent because one of the recipients was rejected by the server. The rejected e-mail address was 'palavsachin27@hotmail.com'. Subject 'Test1', Account: '224.144.109.51', Server: '224.144.109.51', Protocol: SMTP, Server Response: '550 5.7.1 <palavsachin27@hotmail.com>... Relaying denied. IP name possibly forged [224.144.40.210]', Port: 25, Secure(SSL): No, Server Error: 550, Error Number: 0x800CCC79"

224.144.109.51 -- linux Server and 224.144.109.210 -- Firewall
I have allow every thing on firewall for linux and I have configured Sendmails MTA to operate on 224.144.109.51.