Small employers hiring around Boston (Boston)

A friend who works at a local manufacturer says there are openings not advertised online. There are 4 people counting on me, so I am trying to be careful. One is a print shop, one is an accounting firm and one is a clinic. What do you write in a cold email?

A short email with two sentences about what you can do and your résumé attached worked for me. I followed up after a week.