A device for inserting sheets into an envelope comprises a holding device supporting the envelope. A support portion of the holding device is inserted into the envelope. The support portion has a fixed orientation and position relative to a feed device. The device further comprises a mechanism for preparing the envelope for accommodating the support portion of the holding device. The mechanism is upstream of the holding device and comprises a first interaction device, acting onto the envelope in a first direction during feeding of the envelope and a second interaction device downstream of the first interaction device, acting onto the envelope in a second, opposite direction. The second interaction device comprises at least one cam on a rotatable shaft. By rotation the shaft and cam may be brought into an interaction position, with the envelope, or an inactive position.