Create a Meeting in the Outlook Web App
To create a meeting directly from an email in the Outlook web app, click on the email so it’s open in the preview pane or double-click the email to open it fully. Click the three-dot menu icon in the top right-hand side of the email and select Other Reply Actions > Reply All By Meeting.
A new meeting request will open with the contents of the email in the body of the request and the recipients as attendees. Anyone in the “To” field of the original email will be a Required attendee, and anyone in the “CC” field will be an Optional attendee.