No. Internet gambling is illegal under state law. Online sites may advertise they are legal  and licensed  forms of gaming. They may be legal or licensed where the bets are received, but it is illegal to place bets from Mississippi with these businesses.
The BetMGM Online Sports Betting app is available in Arizona, Colorado, Illinois, Indiana, Iowa, Kansas, Louisiana, Maryland, Massachusetts, Michigan, New Jersey, New York, Ohio, Pennsylvania, Tennessee, Virginia, Washington D.C., West Virginia and Wyoming.