I don't have privilege to use Office365Outlook, so I tried this with gmail SendEmail(V2) and it is working fine for me. I created small flow to call from button. I am getting 5 emails for each item from the gallery on pressing button.

Created Flow with two parameters subject an body.

Then Used Send email action for Gmail as shown in below screenshots

Add the flow in app as shown on left side and then On SendEmail button call the flow.