Doumbe, who joined the Dons from Plymouth in August 2009, will become a free agent when his contract expires next month.
The 33-year-old Frenchman made 141 appearances, including 28 this season, for the club and scored 11 goals. He was also part of two play-off campaigns under current Dons manager Karl Robinson.
"Mathias has been an excellent servant to this football club and has proven to be a tremendous professional," said Robinson. "He is a strong character who has played a large part in our recent history and it was a hard decision to release him this year.
"However, with the Financial Fair Play regulations becoming even stricter this season we have to be prudent with our recruitment policy and along the way we will have to make tough decisions.
"I would like to thank Mathias for all of his work and dedication to the club over the past few years and wish him the best of luck in the future. He is someone I class as a friend of mine and he will always be a friend of the football club's."
Meanwhile, Otsemobor and MacKenzie are now contracted to the club until June 2014.
Captain Dean Lewington, fellow full-back Adam Chicksen and goalkeeper Ian McLoughlin have been offered new deals but the trio have yet to put pen to paper.
- Sports & Recreation