Hmmm... Do we want to think of the open letter as ET's first publcly released document? Then it should be accompanied by a press release...

What is the proper way to do this?

The open letter is addressed to Piebalgs and Wallstrom.

We can also copy others explicitly (in a CC: field, such as, for instance, the EP committee on Energy, and maybe someone from the Council, that would have to be the Finnish minister in charge of Energy policy).

Then there is a wider distribution list of MEPs and national politicians? (not named on the letter) These people would require some sort of short cover letter to introduce the document we're sending them, since they're not addressees.

And then there is the press...

Should the letter be released here on the ET website and a press release sent to media outlets on top of that? The open letter would have to be submitted with a cover letter in any case.

Nothing is 'mere'. — Richard P. Feynman