Your end users will soon be able to add and remove delegates from within Outlook for iOS and Outlook for Android. Delegates will be able to access those mailboxes on their mobile app as well.
When this will happen
Rollout begins in late April and should be complete in early May.
How this will affect your organization
A delegate mailbox is a mailbox where users can provide access for others (delegates) to take actions on their behalf.
With this update, users can manage delegates from within their Outlook mobile app. Colleagues with delegate permissions can add and view delegate mailboxes in their Outlook mobile app.