If you call your Recruiter "Sir", you'll likely get slapped upside the head. "Sir" is for officers; enlisted Petty Officers WORK for a living. Don't ever lose sight of that distinction.

Everyone has their own protocol - if you're not Navy, ask him/her how they'd like to be addressed. If it's a Chief/Senior Chief/Master Chief, then you address them as Chief, Senior Chief, or Master Chief. If it's a First Class, Petty Officer or first name will do.

Raven gave a good answer. For emails address them by rank also, but this can be shorten, Petty Officer is PO. If they are an Officer start with Sir/Ma'am.

How did he tell you to address him? I would go with that and if he hasn't stated a preference go with Petty Officer (insert last name here) until he does- and unless he is an Officer, DO NOT (for you own safety) call him Sir......

Call them Petty Officer _____ or what ever their rate is and their last name. So my recruiter is AD1 so and so lol. Sir/Ma'am is only for officers! No difference!

Your Highness

And last name

if you are trying to get in, you call him (or her) GOD...because they hold your future, in their hands!

"What's up Squid?"