What is your opinion on using "Dear All," in business emails when addressing to a group of people? Is this too informal? Or has it been an accepted usage?

The situation is that I know all the recipients but I can't find a simple term that can represent all of them. The recipients include my colleagues and external parties. There are a number of alternatives but I think none of them fits in the situation.

Dear Sirs - sexist
Dear Ladies and Gentlemen - seems too formal and outdated
Dear Colleagues - not all of them are colleagues, some are external parties
Dear (name of committee, etc.) Members - not all of them are members

Do you have any other suggestions?

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Comments  (Page 4) 
'Good noon' is not an English expression.
Why not use "partners" for service providers?

"Dear colleagues and partners,"
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Consider this.
I have a service provider, but this is not my partner.

 LisaM's reply was promoted to an answer.
how about "Dear All Colleagues" is that not a compromise?
Students: We have free audio pronunciation exercises.
'All' is redundant.
Depending on the situation, I use any of the following salutations in my e-mails: Good Morning Everyone, Greetings Everyone, Greetings, Salutations, Hello Everyone, and Attention Everyone.
I work at a university and it is common practice here to use "All" but I'm not a big fan of that, therefore, u
sually skip the salutation state my business.
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How about "Dear Everyone"? At least everyone is a noun...
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