Want to send mail to Intranet Machine?
 

I have a sendmail server configured with two users created internal to company domain intinfra.com.
All I want is send mail from Gmail Account directly to that particular User. What need to be done to reach mail from Gmail to internal Machine.

If I'm understanding the question, you need to:

1) login to your gmail account (or the one you want to forward messages from)
2) Click on "settings" on the top right of the page
3) Click on 'Forwarding and POP/IMAP'
4) Click the radio button next to 'Forward a copy of incoming mail to' and enter the email address you want to forward to.

Not Exactly...

I have a Sendmail Server configured internal to my company domain called intinfra.com.I have two users called sender and receiver created.So its obvious they will have thier mailbox created Right? Now what I want is Open Gmail Compose Mail option and type directly sender@intinfra.com somewhat kindda entry and it should reach directly to my mailbox.I too need it to put in Public IP i Guess.
Pls Suggest?

Yeah. You're correct. You either need to put your mail server on a public IP or have another machine that has a public IP that relays the mail to the internal mail server. The first is easier and cheaper. The second is generally more secure.