In a cloud-only Azure AD & Office 365 setup (in other words, no AD DS and no ADConnect), I have several security groups with assigned membership. I would like to mail-enable these.
The users who are members of the groups all have Office 365 licenses assigned to them and can send and receive mail fine.
I can create a new mail-enabled security group in the Office 365 portal but I can't see any way to mail-enable existing groups.