Hi, I'm John! I will help you with this.
This can happen if the system detects unusual activity, or if your account hasn’t been fully verified.
For personal accounts, the best place to start is making sure your account is fully verified, check that your security info (like your phone number or alternate email) is up to date at https://account.microsoft.com Once that’s done, the limits often lift within 24 hours.
For more detailed guidance please see "How can I increase sending limits?" section here: https://support.microsoft.com/office/sending-limits-in-outlook-com-279ee200-594c-40f0-9ec8-bb6af7735c2e
I really hope this information is helpful! Let me know if you have any further questions or concerns.
Regards,
John J.D.