Using Classic Outlook on Windows for personal email, calendar, and contact management
Thanks for the details. Is your account new or have you recently added many new recipients?
For personal Outlook.com accounts, there’s a daily limit on how many recipients you can email, and sometimes sending to a group of 28, even a few times a week, can trigger a temporary 24‑hour block. The best approach is to wait for the block to lift, then send to smaller sub‑groups instead of all 28 at once, keep your sending pace steady, and avoid sending many emails rapidly. If blocks continue despite normal use, check your account for unusual activity and make sure it’s secure.