If you are mailing something other than a post card, the first huge problem in direct mail is getting the envelope opened.
Many people (I’m one) do their mail over the wastebasket.
There are many proven techniques for increasing the likelihood. One of them is to do everything possible to make it look like some kind of official document – one you’d better open.
The problem with that of course is once it is opened and they see it is NOT a lawsuit or a threat from a government agency, where are you then?

The links in the marketing chain are fragile. They are steps building credibility and interest.
Don’t blow it.