Planon calculates whether a mailbox subscription is lost. The assumption is that the subscription is lost if the last notification date (Reservations> Exchange Mailbox) and the time set for Exchange to deliver the notification (System Settings > Exchange) are before the current date-time.

A lost subscription is indicated by an alert icon next to the mailbox in the element list.

When the maximum number of attempts to resubscribe a mailbox is reached, it will be indicated by an arrow-right-line icon next to the mailbox in the element list.

Unsubscribed mailboxes also appear on the Lost Exchange Subscription step.