Do most company email infrastructures (e.g. Exchange Server) support and/or use SMTP to send email? One of the requirements of my application is to send status emails from the application. Is it enough to support SMTP or should I be looking at some other protocols as well?
The first part of your question belongs on serverfault. However, I'll answer here.
Q. Do most company email infrastructures support and/or use SMTP to send email?
A. Yes, ALL of them do. That's how email is sent... at least to external servers. Internally, mail servers just shuffle the mail between local accounts, which is proprietary and usually not exposed for any other purposes.
Q. Is it enough to support SMTP or should I be looking at some other protocols?
A. How else would you send email? (Rhetorical)
You might be thinking about POP3 or IMAP. Both of which are used by clients to contact a server to receive emails. However, everything uses SMTP to transfer mail around.