How do you greet multiple recipients in an e-mail?
Assuming they're both male, I just use "Sirs", but it seems a bit informal.
If you don't know the recipients' names, I refer you to the other answers. However, if you do know their names, then I will add that I would actually just write:
I have been using this formula for more than a decade. So far, nobody has complained. For me, this approach has quite a few advantages. First of all, it is more personal than simply "Greetings" or "Hi all". Secondly, if one of those people is the main recipient and the other is CC, or if one of them has a higher rank (say, he is the boss of the other), I can reflect that in my address by mentioning him first. Lastly, this formula can be easily adapted to many situations. If some (or all) of the recipients are female I simply write:
If I need to make it more formal, I simply write:
Dear Mr. Smith,
Dear Ms. Black,
And I can easily extend it to three or even four people:
Dear Mr. Smith,
Dear Ms. Black,
Dear Mr. Blunt,
Now, when I am addressing more than four people, I often do use something like "Greetings", "Hi everybody", "Dear clients", "Dear colleagues". However, even then I sometimes set the most important recipient apart by writing:
Dear Prof. Black,
Dear Mr. President,
Dear Members of the Committee,
If I am addressing a few people who are well known to me, I would generally use:
Dear John, Bill, Jack,
If I am addressing a lot of people, or people who are not familiar to me, I would go with:
I rarely begin emails with a salutation. If I do, it is usually just the name - I have never transferred the pointless 'Dear' to emails.
If I wanted to put one in a group email, I suppose I would start with a word like "friends", or "people", or "folks", depending on the context and formality.
It's kind of a carryover from my medievalist hobby, but I really like using
for emails to a group of people. It's also really handy for addressing a single person when you're unsure of that person's gender and/or title.
If you are working together on a project, then I rather like
This can be appropriate even if the recipients include people from both your company and the client. It's a subtle reminder that you are all working towards a common goal.
More generally, I'd just use
"Sirs" is just completely wrong. If you are addressing more than one man, it would be "Gentlemen".
I have been using, "Hello to all". It seems to work well for both male and female recipients and is formal enough to use in a business setting.
Email is still sufficiently young that formal conventions have not emerged. I find it useful to imagine myself in the mind of the recipient and ask what information I need to give them in the greeting.
If the email is really to be sent with equal priority to a number of recipients and they regard themselves as part of a group (fellow developers for example), then I would use
If, actually, the email is a mailshot to a number of individuals who don't know each other, then its an individual email.
Dear Sir (or Madam),
Here, I prefer to use the convention that Sir is neuter.
And lastly, if an email is really to a single individual, but with a few more individuals copied in (such as a question to an individual developer, but where I want the email trail to be visible to the group), then I would use
Dear Bob (Alice, Charlie, Dilbert)
The last one is not a convention I have seen elsewhere, but I find it works for me.
If it is a formal letter, then you can use 'Dear Sirs' but if it is informal, simply 'Hi' is fine. 'Hi' addresses either one person or many, the same as 'you' refers to one person or many. I would not ever use 'Gentlemen', but I am from Australia where our English is more informal.
I usually just use the words
You can also use gents to refer to many recipients.
I agree with louiser89 and I will add that - even though many people or perhaps most people don't think that "Dear" is appropriate on emails - I will continue to use "Dear" or, in my language, "Caro (Cara)". It is not only because we have always used it in letters and in commercial correspondence; it is not just traditions. "Dear" is a nice word, it is gentle and polite. It is not a word that could ever offend anybody. And it is certainly not formal, unless you consider formal the people you love or that you consider your friends, or the people you like. So why not use it also in emails? How can something nice become formal or old fashioned or, worse, strongly disliked? Of course we should never consider it obligatory, but why be against it? Dear Friends, don't be too angry with me: English is not my language, but it is a very "dear" language to me for many reasons.