A divert assembly is described for a mailpiece sorter operative to sort mailpieces into one of a plurality of sortation bins. The divert assembly comprising a re-direct mechanism for selectively re-directing mailpieces travelling along a feed path into the sortation bin and causing each selected mailpiece to be re-directed at an angle relative to the stack of mailpieces to be accumulated in the sortation bin. The divert assembly also including a stacking assembly including a Leading Edge (LE) urge roller, a support blade, and a Trailing Edge (TE) alignment device. The LE urge roller accepts and urges each of the selected mailpieces toward a sidewall of the sortation bin while the support blade holds each of the selected mailpieces between the urge roller and the support blade and in an on-edge parallel relationship relative thereto. The support blade is moveably mounted relative to the LE urge roller to allow the accumulation of additional mailpieces between the LE urge roller and the support blade. The TE alignment device includes a stepper motor rotationally driving a cam about a rotational axis. The cam defines a surface operative to urge the trailing edge portion of each selected mailpiece toward the support blade and into alignment with the stack.