Reche Caldwell -- Ex-NFL Player Pleads GUILTY To Mailing Molly

Former NFL wide receiver Reche Caldwell now admits he shipped and received more than a kilo of molly through the mail -- and he's facing SERIOUS jail time for it.

Caldwell pleaded guilty Wednesday in Tampa to possession and intent to sell a huge stash of ecstasy pills, according to the U.S. Department of Justice.

Prosecutors say the plea was part of a deal Caldwell hammered out with them -- but details of the deal were not immediately released.

As we told you ... Caldwell was busted in May for trying to send 2 separate packages in the mail filled with the party drug. The ex-Chargers, Patriots, and Redskins player faces up to 20 years in federal prison. That's the max, but considering he worked out a deal ... that seems unlikely.