Not possible. A user with full access can delegate specific folders, but can not give full access or send as access without some admin level perms.
Give a user management rights to shared mailbo
Rajko Albrecht
1
Reputation point
We want to give users in O365 the ability to manage specific shared mailboxes without giving them exchange admin rights. Eg, a user should be able to add or remove other users, set their rights for "Send as" and so on.
But all I read is that such a user has to be an exchange admin - is this really right? Or miss I something where a non-exchange admin can manage user for one specific shared mailbox group?