Abbey was one of six players released by Roberto Di Matteo this week and made just five appearances for the club in his two-year stay as understudy to Willy Gueret.
He told the club's official website: "Willy Gueret has had two fantastic seasons and performed with great consistency so I've got no complaints whatsoever.
"I'm now starting a new chapter in my career, hopefully with another League One club so I can come back to stadium:mk and say thank you to the fans.
"They are as good as any supporters I have played in front of."
Source: Team_Talk