sending email via mail server

hi everyone

i am facing one problem.
there is one unix server in our organisation which stores daily routine backup, and one mail server which is on windows 2k3, they are on one intranet.
now i want that a mail should be generated and sent to the e-mail id of employees like nitin@hotmail.com and so on from the unix server.
obviously the mail will go via win2k3 mail server.but how????
the main problem is that how to make SMTP Connection between the two servers.

Parmeet,
I don't understand why people don't write detail mail for the solution they lookin for FREE. Specific to N/W related queries, engineer/admin like to have an ASCII diagram for better understanding. Also you MUST mention all software and integration running on specific OS.
No body in this world can help you with your write-up.