Hi @sanjana12 ,
Few possibilities, One when a operator manually 'stop' the delivery, the status changes to 'Delivery cancelled'.

Other possibility is, In delivery's property > validity tab you can assign a delivery validity period duration. In the below screenshot, its 5 days.

For the recipients who are unreachable, retry will happen for 5 days.
On 5th day the delivery will get expired and status of the delivery changes to 'completed' by the cleanup task. Parallelly, For those recipient whose status is on 'pending' / retry was happening, Retry will stop after this validity period and the status of the recipient in broadLog schema changes to 'Delivery Cancelled'.
So in general, If the delivery log record is either pending or in retry or waiting for the contact date to be reached, but the delivery is canceled either manually or by reaching the delivery expire period, the status will change to 'Delivery Cancelled'.
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