What is the polite way to start off an email which is not addressed to a specific individual?
In the states I might use a friendly, Hello, or Good day in the space for Salutation. The body of the email follows in a separate paragraph.
A polite way is just to use a phrase you would use while writing a formal letter, e.g.
Sehr geehrte Damen und Herren,
works fine. As suggested here, if you know the recipients and are on friendly terms with them, a less formal way would be to start with "Guten Tag".
You never go wrong with
Sehr geehrte Damen und Herren,
like Glorfindel mentioned.
An alternative for a non-formal greeting would be
but I would only use it for something like sending out the tornament plan of your local soccer club.
Another possible greeting would be, if you address a certain group of people:
Liebe or Werte "Group you want to adress"
Werte Mitglieder, / Liebe Studenten,
It's still non-formal, so be careful with it, like adressing coworkers you don't know very well with
is usually only done when inviting to a company event or for close coworkers you all know well.
While "Sehr geehrte Damen und Herren," will certainly work and is traditionally the correct thing (in "real" letters), I deem it a tidbit stiff for e-mail. For a written letter, there's no doubt, but for e-mail, I don't know, not sure.
For e-mail, unless it is explicitly my intent to sound formal (complaint letter, termination notice, etc.), I'm often just using "Hallo," nowadays. Nothing wrong with that.
If I happen to know the recipient's name, and I'm not closely acquainted with them, I may address them personally with "Sehr geehrte Frau" oder "Sehr geehrter Herr", that works.
The simple "Hallo", optionally followed by the name is much less formal, less bothersome, and fewer characters to type.
Since you said "in the states", please do note, by the way, that either way the salutation terminates with a comma, which is noteworthy as you do not capitalize the first word of the following line (as you probably would, and as the e-mail program might automatically do).
Formal greetings in an e-mail (unless they come from an institution) are, in my perception, a bit like getting a SMS ending in "Beste Grüße". You can immediately tell with high confidence that the sender is over 70 years old and hasn't understood the the meaning of the first "S" in "SMS". Not like it's wrong, it's just... well, odd.
Plus, "Hallo," has the advantage that it leaves very little doubt about being politically correct in a country so full with queer ideas where normal is abnormal and where people spend such a large part of their time pointing that out.
In a time where you get eyeballed when you forget to append "und -innen" to an obviously gender-neutral word which happens to carry a male article with no particular connotation in the German language since approximately a thousand years, where "Divers" is an official gender, and where the 4th largest city in the country plans to no longer have toilets separated by gender in high schools, you cannot really be sure any more what's right and what's wrong and how to correctly address people. Right, we do not have any more urgent problems to solve.
O tempora, o mores.
If you can't address a group of people as mentioned elsewhere you can also address the company or department you write the email to.
Sehr geehrte Firma xyz
Sehr geehrte Vertriebsabteilung der Firma XYZ
Sehr geehrter Musikverein
Sehr geehrte Stadtverwaltung
This gives your greeting a more formal form than only hello but still has a relation to the receipients.
If you get a response from a person with individual name and mail address you can greet this person by name in your following email.