Group mail history track

Dear supporter,

I just migrated our mail service from Gmail to Office365.

I created a group mail in Office365 however forget to put the member of  mailbox under that group in 3 days.

So there is no member under the group in 3 days,

Is it possible that I can find who and what mails already sent to this group. thank you. I really need to track the 3 days history for this group.thanks.

Best Regards,

Joey