The Groups Accepting External Email report shows you which Distribution Groups within your Microsoft Office 365 environment accept external mail. The pie graph displays how many of your Distribution Groups accept only internal messages - Groups that accept external email have the RequireSenderAuthenticationEnabled attribute set to false.
The Data Table
The data table lists the names of the Distribution Groups and their email addresses. You can add, remove or re-order these columns to display the information in a custom way.
As with all of the reports, this information can be customized, filtered and scheduled.