How to address letter to multiple recipients?

[seirk]

Hi,
We are in the midst of a debate in my office over the proper method to address a business letter to multiple recipients. Listed below are the few suggestions we have come up with:

1. Dear Messrs
2. Dear Sirs
3. Dear Mr. X and Mr. Y

I have no idea which one is appropriate and I am trustful that the user’s knowledge on this forum will guide me in the correction directions. Many thanks!!

Chris

[Tdol]

The possibilites I know of are:
Dear Sirs or Dear Sirs/Mesdames (looks a bit old-fashioned)
Gentlemen (used without 'dear'- I have seen this form used in American English, and remember it because it struck me as very odd as a British English speaker)