important : Can I use Mac system fonts when making a 'logo'?

You are speaking to a user to user forum with Apple moderation. We are not experts in Apple's trademark/copyright.

For that you'll need to visit http://www.apple.com/legal/ and discuss with the appropriate team.

In addition, I offer the following. First, assuming that is is ok to use the font which Apple provides, it is important to understand that the recipients may or may not have your selected font installed in their computer (if t is not an Apple computer). Whatever document you sent the logo in may therefore be displayed with a substitute font. Generally, it will look much the same - but not always. However, if you create the logo and then save it as a picture of one type or another, it will not change when it is impeded in your document. I hope this is helpful.