Figuring out how to start an email can be a real challenge.

Is "Hey" too casual? Is "Dear" overly formal? Is "Morning!" too cheery?

If you're thinking the email greeting isn't all that important and that it's silly to over-think it, you're wrong. How you begin an email sets the tone and may shape the recipient's perception of you. It may also determine whether they keep reading. So, yes, it's very important.

"Many people have strong feelings about what you do to their names and how you address them," Barbara Pachter, a business-etiquette expert, tells Business Insider. "If you offend someone in the salutation, that person may not read any further. It may also affect that person's opinion of you."

We had Pachter and Will Schwalbe, co-author of Send: Why People Email So Badly and How to Do It Better, weigh in on a handful of common email greetings.

The perfect way to start an email will depend on to whom you're writing, but in general, when you're writing a business email to someone you don't know well or at all, the experts say there's one safe choice — and a bunch you should usually avoid:

WINNER:

'Hi (name), ...'

If you want to make it a little more formal, you can always use the person's last name: "Hi Mrs. Smith, ..."

"The reason I like this one is that it's perfectly friendly and innocuous," says Schwalbe.

It's also Pachter's favourite. She says it's a safe and familiar way to address someone, whether you know them or not.

So when in doubt, go with "Hi."

GREETINGS TO AVOID IN MOST SITUATIONS:

1. 'Greetings, ...'

This is a good backup to 'Hi, (name) ...' if you don't know the recipient's name. But you should always do whatever you can to find out that information.

2. 'Hey!'

This is fine to use with your friends, but the very informal salutation should stay out of the workplace. It's not professional - especially if you're writing to someone you've never met, says Pachter.

Schwalbe agrees: "I can never get out of my head my grandmother's admonition 'Hey is for horses'."

Also avoid "Hey there." It tells the person, "I don't know your name, but if I try to sound cool and casual, maybe you won't notice."

3. 'Dear Mr./Mrs./Ms. (last name), ...'

The 'Dear' family is tricky because it's not always terrible or wrong to use, but it can sometimes come off as a bit too formal.

4. 'Dear (first name), ...'

Again, it's not the worst greeting in the world, but it's a little old-fashioned.

5. 'Dear friend, ...'

"If you don't know my name, or can't be bothered to use it, we probably aren't friends," says Schwalbe.

6. 'Dear Sir or Madam, ...'

Way too formal!

Plus, this salutation tells the recipient that you have no idea who they are, says Pachter. "Why then should the reader be interested in what you have to say?"

Schwalbe adds: "This one is very stiff. It always feels like bad news or a complaint will follow."

7. 'To whom it may concern, ... '

The recipient might think 'OK, this doesn't concern me ... I don't need to continue reading.'

It's also a cold and very impersonal way to start an email message.

8. 'Hello, ...'

Not bad, but a bit informal if you're addressing someone you don't know very well.

9. 'Good morning/afternoon/evening, ...'

It may not be morning, afternoon, or evening anymore by the time your email reaches the person - or if they're in a different time zone - so it's best just to skip these.

10. 'Mr./Mrs./Ms. (last name), ...'

Another stiff and abrupt one. The recipient may feel like you're about to reprimand them.

11. '(First name)!'

First off, it's a bit informal and abrupt. Then when you tack on the exclamation point, it just gets annoying.

"It's a bit jarring right off the bat - like someone is shouting at me," Schwalbe says. "Even without the exclamation, it's a bit abrupt. Better to precede the name with 'Hi' than just blurt it out."

12. 'Yo!'

Do we really need to explain why this one is a no-no?

13. '(Misspelled name), ...'

Spell the recipient's name correctly!

"Many people are insulted if their name is misspelled," says Pachter. "Check for the correct spelling in the person's signature block. You can also check the 'To' line. Often, people's first or last names are in their addresses."

14. 'Gentlemen, ...'

It's sexist, Pachter says. If you're addressing a group of people, say, "Hi, everyone."

15. 'Happy Friday!!!'

You don't want to be overly enthusiastic. It's not professional and sets the wrong tone. Plus, it might get under the recipient's skin.

16. 'Hi (nickname), ...'

Don't take it upon yourself to call William "Will" or Jennifer "Jen". Unless the person has introduced themselves using a nickname or uses one in the signature of their own emails, stick to their full name.

17. 'All, ...'

This one sounds abrupt.

Again, if you're writing to a group, use "Hi, everyone."

18. 'Mr./Mrs./Ms. (first name), ... '

Pachter says this is how young children address their teachers: 'Mrs. Susan, can you help me with this maths problem?' It's not appropriate in the professional world.

This story first appeared in Business Insider. Read it here or follow BusinessInsider Australia on Facebook.