"SMTPSENT.BARELINEFEEDSAREILLEGAL" NDR RECEIVED BY EXCHANGE ONLINE OR EOP USERS IN OFFICE 365 DEDICATED/ITAR Supporting Microsoft Article: https://support.microsoft.com/en-gb/kb/2998901 ...
A useful article to keep in mind. How this could affect your users abilities to access the archive services where Azure AD Synch and authentication is in place: https://dzone.com/articles/azure-a...