Automated script once user send email to UNIX server

is there any possibility to trigger a script. once the user send email to the unix server box with specific subject line. My script will search for the specific word in the unix email and run the shell script if the specific keyword is sent in the email to the unix email box. so that it can automated. not sure how to check in the unix email box.

man procmail

procmail - Wikipedia, the free encyclopedia

If you're using sendmail as your mail server, look at the man pages for "vacation" along with "sendmail".

I am using HP UNIX. I need to check on daily basis whether I received any emails on the unix server. if particular emails received I will be executing my shell script. any idea how to check the emails on the unix outlook server.