The 33-year-old, who joined the Shrimpers in 2010, was under contract until the end of the current season, but he is now free to find another club after being told he would not feature in Phil Brown's plans.
Brown told the club's website: "I just felt the time was right to try and move this club forward and unfortunately for Chris he wasn't going to be part of those plans.
"He has been extremely professional since we spoke about the upcoming season and has continued to work extremely hard in training.
"He's had an excellent career with Southend and has been a big part of the club for the past three seasons. I know the fans truly appreciate the efforts he has put in since he joined in 2010.
"I would personally like to wish him all the best for the future."