Cross-premises mailbox permissions supported in hybrid environments (Q2, 2018)

Without any big announcements Microsoft started rolling out support for cross-premises mailbox permissions.

The following cross-premises permissions are supported:

• Full Access
• Send on Behalf of 
• Private items 

The following cross-premises permissions or capabilities aren't supported:

• Send-As
• Auto-mapping
• Folder permissions

Feature ID: 16136

Technet