Here’s a great piece by Matt Handal about proposal cover letters.
The most important part is the first:
“Don’t include a cover letter in your proposal. It’s not going to convince us. So, don’t waste your time.”
Why would he say that?
He said that because he’s seen hundreds, if not thousands, of cover letters and they all said nothing.
As I wrote a couple of weeks ago, respect your time and respect your prospects’ time and make the whole process as quick and easy as possible.