Adding external contacts to Office365 group

Hi all,

did i get it wrong or is it impossible to add external email addresses (even after adding them to the contact list) to office365 groups (note, NOT distribution group)?

Saw the option to let people outside organization email the groups, but for that i need to leave it public (which i don't want to). It also doesn't give an option to review all the previous data, it just works as a regular distribution group.

Such a thing is possible when using google apps, was expecting it to be the same.

Thanks!