The Tractor Boys came second in the Championship under manager Kieran McKenna.
However, they will have to do without several players from that squad, as they are not renewing their deals.
Omari Hutchinson (Chelsea), Kieffer Moore (Bournemouth), Jeremy Sarmiento (Brighton), Lewis Travis (Blackburn) and Brandon Williams (Manchester United) were all on loan for the season.
Kayden Jackson, 30, and Dominic Ball, 28, have been released at the end of their deals.
On their departures, McKenna said: "Kayden and Dominic have both been important members of a group which has achieved significant success over the last two seasons.
"Both have made vital contributions on the field and, off the pitch, have played central roles in developing a culture and setting standards which have been so important to the club's progress.
"Their contributions to everything the club has achieved should not be understated.
"I am certain both Kayden and Dominic will be real assets at whichever clubs they take the next steps in their careers and they will always be welcome at both Portman Road and Playford Road."