Windows has exchange server, CDO, CDONTS, MAPI etc, Linux has sendmail, SMTP ...

You are confused here, or at least on a module-overuse binge :)

We don't need a unified mail interface at all. Linux doesn't "have" SMTP. SMTP is "Simple Mail Transfer Protocol" and is the protocol that all mail (even on Windows), wants it escapes the evils of MS Outlook and the like, speaks with. If you want to send mail, use a pure perl module that speaks SMTP protocol. Even exchange boxes usually accept SMTP input from internal machines, ex: mailhost.yourcompany.com