Maintaining muscle mass

No. There is no guaranteed formula to assure no muscle loss, but 1200 is way too low for any typical-sized man, and will seriously risk it. 1500 is the minimum MFP will recommend for any man, and it's really only reasonable for someone smaller, pretty inactive, and maybe older.

(I'm a woman, 5'5", and lost most of 50ish pounds in under a year at age 59-60 on more than 1500!)

If your priority is weight loss with muscle retention, set up MFP with a weight loss goal of no more than 1% of current weight weekly (slower than that is less risky, and for sure recommended if you have less than maybe 50 pounds to lose), eat back a reasonable estimate of exercise calories, strength train faithfully with a good progressive program, eat sufficient protein (and generally good overall nutrition), and be patient. That would be your best bet.