Swiss people typically add a personal touch to all kinds of actions, and that includes notes and memos such as e-mails. They would always start out with "Lieber Andreas" ("Dear Andreas") and end on "Viele Gruesse" ("Best regards") or something similar. Omitting those elements might carry a message to you.
In contrast, it is rather unusual to have such "folklore" in e-mails exchanged between Americans. It is largely regarded as redundant. Finding a post-it sticker on your door with a note that does not carry any addressing nor signature is considered normal (assuming that you would know anyway who wrote the note).
Notice in Switzerland how people greet you, be it in the hallway or in the gent's room (I can't comment on ladies' rooms). You will almost always be greeted by name, "Sali Andreas", or "Gruezi, Herr Krause" ("Hello Andreas" or "Good day, Mr. Krause"). If you don't know someone, for example when you show up at a party, you would surely walk over to the person and introduce yourself. On leaving the party you can then say farewell to the person and utilize his or her name. The flip side is that if you don't address someone by name, you can safely assume that the other person will think you forgot his name.
Cultural cross-fertilization has shown some merits, at least in my company. Most people here in New Jersey now open their e-mails and notes with a greeting and conclude with at least putting down their name. Interestingly enough, when someone joins from another American company, you often get to hear a comment about them being surprised by the "personal touch" in e-mails and notes in this company.
Still - the question remains how to address someone. I recall from a long time ago when I moved from Germany to Switzerland that being addressed by "Lieber Andreas" struck me as surprisingly personal. Germans would rather use "Hallo Andreas" ("Hi Andreas"). Exactly that discussion took place in a group meeting at my workplace some fifteen years later.
A colleague brought up the discussion and pointed out that to him being addressed by "Dear" would actually carry some romantic connotation, and he was confirmed by others. I followed a couple of e-mails over some time and noticed that there is indeed a clear pattern. To cite just one example, a current project team consists of four people, Bill, a Scotsman, Dean, an Englishman in Basel, Garret, an American in California, and myself. Over at least 20 e-mails you could observe that Garret would always write "Hi Bill" or "Hi Dean", whereas he would always be greeted with "Dear Garret".
I hope you learned a bit about how greetings are perceived and how subtle differences can be read very differently.
AndreasP.S. If you wonder about the title of the story, "Dear Jerry": Jerry is my boss and he confirmed that being addressed by "Dear" strikes him as a bit strange, at least in the workplace. So dear Jerry, take it as a promise that this is my last glitch.