Dear Dr. Kirk:
So what's the protocol with the initials? Do you put MBA after your name in your signature line?
Recent MBA graduate
Dear MBA grad:
Typically only Ph.D.s or M.D.s do this. Or someone might put an earned certification such as CPA or SPHR on their business card or signature line but putting MBA is considered inappropriate.
However, you can certainly mention your newly earned degree on your website or blog and on a cover letter in a job application. Here's an article that discusses this further.
Congratulations on your accomplishment!