According to Daily Mail Australia, Michael sent an expletive-laden message where he didn't mince his words about the man who Stacey has moved on with.
"I'll give you this, you are a good looking c**t. Though, know I like you. You will see [it] will take an army to rock me," Michael began the alleged message.
"Make sure the bullet goes straight throw [sic] my head."
"Because I'll fly charter a jet with the hardest c**ts from Russia just for the banter," Michael's message continued.
"Trust me to stay your distance. Bikies wanna go me, wear their true colours, I'll always respect the lads."
During Sunday night's MAFS finale, Stacey posted videos to her Instagram stories where she revealed she was watching with her pal, Anthony.
"He's a pig and the text message he sent me last night proves it," Anthony said in one clip, as Stacey nodded in agreement.
Anthony, it appears, was referring to the threatening alleged message Michael had sent via Instagram.
Stacey also spoke out about Michael, calling her ex 'husband' a "pig".
Michael has moved on after the show with fellow contestant, KC Osborne, who was 'married' to Drew Brauer in the experiment.