Dear Chris Moore9;
Good day! Thank you for posting to Microsoft Community. We are happy to help you.
Based on your description, I understand that you have a concern with "best app to send a newsletter or event announcement to a group larger than 50 members, Any suggestions?"
Microsoft offers a solution for sending newsletters or event announcements to a large group of people through its email marketing service called "Microsoft Dynamics 365 Marketing." This service allows you to create and send professional-looking emails to a large number of recipients, track their engagement, and manage your subscriber list. Refer to Microsoft Dynamics 365 Marketing customer journey orchestration preview now available - Microsoft Dynamics 365 Blog
To transfer your existing 50 group member list to this service, you can export the list from Outlook and import it into Dynamics 365 Marketing.
Other popular email marketing services that you can consider include Mailchimp, Constant Contact, and Campaign Monitor. These services also offer similar features and allow you to send emails to a large group of people. However, you will need to check their pricing plans and features to determine which one suits your needs best.
I hope this helps! Let me know if you have any further questions or concerns. Please note that our initial response may not always resolve the issue immediately. However, with your help and more detailed information, we can work together to find a solution. Thank you for your help.