Re: Need help with Auto Reply from shared mailbox
Hi @estinson
Thank you for posting.
According to your description, you would like to auto-reply email once new email arrived in a shared mailbox. Meanwhile, you want to send reply email via a group address. If any misunderstanding, please kindly let me know.
We can try below flow steps to achieve your first requirement.

The hr-user is one of my shared mailboxs. Once tested, I’m able to receive that replied email.


For your secondary query, I am wanting to send using a noreply distribution group. Is that even doable?
I’m afraid it’s not possible as there is no action or trigger for group. Meanwhile, if we want make shared mailbox send as a group. We need to first configure SendAs permission in advance from exchange admin center. However, it’not supported to assign SendAs permission to a shared mailbox in exchange. I tested but failed. I couldn’t even find any shared mailbox account listed when I setup group delegation. Thus, I believe it’s currently impossible. It's exchange limitation instead of flow's.
If you still consider use such kind of feature, I recommend you go to exchange UserVoice to post your idea to allow shared mailbox send as a group address.
https://outlook.uservoice.com/forums/907141-the-new-outlook-on-the-web-office-365
Hope the content above may help you.
Best regards,
Anna