Reply settings for Office 365 Groups

Hello,

I have gone through the forum and google, but I have not found an answer to my question. I hope you don't mind sharing a post here. 

Background: User1 (Guest account/outside of the organization) and User2 (inside) are members of the Group1 (Office 365 Group). User3 is outside of the organization, it's NOT a guest user nor Group1 member. The Group1 is enabled with the subscription setting (e-mail sent from anyone to Group1@organization will end up in Group Conversation, User1 mailbox, User2 mailbox).
I would like to achieve the scenario where: User3 sends an email to Group1@organization. User1 (undefined e-mail client) hits "reply" and answers not only to User3, but rather to Group1@organization instead.
I have successfully used feature like that with G-Suite (https://help.lsit.ucsb.edu/hc/en-us/articles/115000974551-Change-Reply-Settings-to-Group-Messages).

How to configure something like that with Office 365 ?

Thanks in advance,
Regards,
Tomasz