Dear PhucPhan,
Thanks for your post in Microsoft Community.
Thanks for your testing.
Regarding your inquiry about lifting the daily email sending limit, it's important for you to understand that Microsoft has implemented these limits to combat spam. Therefore, there is a restriction on the number of emails that can be sent each day. The specific number of emails and recipient limits are related to the usage of your email box, and we cannot provide exact figures, so please accept our apologies (officially, only the subscriber limit is provided for reference: Sending limits in Outlook.com - Microsoft Support). However, a good usage record (meaning full compliance with the relevant content of the Microsoft Service Agreement) can help you increase this limit. If you have reached your daily email limit, we suggest you wait 24 hours before trying to send emails again. You can also bind your account to a mobile phone at https://sms.live.com to increase your daily email limit.
At the same time, it's important to understand that when you are sending bulk emails, each additional recipient is considered as an additional email sent. The number of emails sent is calculated based on the number of recipients. It is recommended that you do not send emails with the same subject to multiple recipients at the same time, or reduce the practice of mass mailing the same email, as this may be identified as spam, leading to your account being unable to send and receive emails normally. Please understand this.
Tip: You can learn more about email sending limits by viewing the Outlook.com page titled "Can't send or receive email in Outlook.com - Microsoft Support"
Finally, I sincerely advise you not to use a Microsoft account (whether personal or corporate) to send a large volume of repetitive emails, as this can easily be detected and restricted by Microsoft, especially if your recipients report you.
Thank you for your understanding! I hope the above response has answered your concerns.
Best regards
Yolanda - MSFT | Microsoft Community Support Specialist