This is the problem, you think you need to address them in any different manner than you address anybody else in business.
I work in i-banking, I have to deal with guys with just a sociology BA to guys who have JD/MBAs from Yale, Harvard...etc. Very few, if any, put JD after their names in cards, or email sig blocks, it's stupid. NONE put MBA.
In fact, if I saw a guy put MBA after his name in an email, I'd circulate it around the office to give everybody a joke for the day.
There's very few acronyms that belong after a name, a CPA, CFA, CFP (or other professional designation), or a JD. Even with a JD VERY few attorneys put it after their name (same with Esq). Actual medical doctors can put whatever they want, as well as their acronyms for professional specialties.
Maybe you're in an industry where such pandering and blatant silliness is paramount, but in the real world, only complete tools put degrees after their name.
Knowing somebody's street cred, as a justification for this stupidity, is ridiculous. Either somebody's got it, or they don't. Putting MBA, MS, or whatever after their name doesn't give somebody cred.
In my personal experience, the people who feel a need to put that stuff after their name (JD, MBA,BA,MS) are the ones who either lack class, went to a lower tier school, or are desperate for attention (or some combination of all).