Sendmail configuration with user mapping on Solaris

Question

I have the following:

• host1.intra.net which has sendmail and users: user1, user2 & user3. It is running SunOS 5.10.
• host2.intra.net which has SMTP server. No authentication, no encryption.
• Email addresses john.user1@company.com, ada.user2@company.com, alice.user3@company.com
• mailx 5.0 on host1.intra.net is being used to send emails

Please kindly enlighten me how could I:

• Configure sendmail on host1.intra.net to use SMTP on host2.intra.net with no authentication, no encryption.
• If an email is sent from the shell of user1, it should appear as being sent from john.user1@company.com.
• If an email is sent from the shell of user2, it should appear as being sent from ada.user2@company.com.
• If an email is sent from the shell of user3, it should appear as being sent from alice.user3@company.com.