The Colts signed Landry to a four-year, $24 million contract in 2013 with the hope that he would be the hard-hitting safety they had been missing since Bob Sanders played for them.
Landry turned out to be a disappointment instead. He was suspended for four games for using performance-enhancing drugs last season. The Colts then placed him on the exempt/commissioner's permission list for a game after he returned from the suspension.
Landry, who finished with 104 tackles and 2.5 sacks in his two seasons with Indianapolis, was scheduled to make $4.75 million in 2015 and $5.75 million in 2016. The Colts will save about $2.2 million on the salary cap by releasing him.
Jackson, the Colts' sixth-round pick in 2014, couldn't stay out of trouble off the field. He had a DUI in June in Muncie, Indiana, and had another DUI last month in Kentucky.
Nixon's time with the Colts all but ended when he missed the team plane to New England for the AFC Championship Game last month.