Hi @shazli7277-7483 ,
According to the official document, Reactions in Outlook only work in Exchange Online mailboxes and, by default, only when the person you’re messaging with is also in your organization and using an Exchange Online mailbox. Therefore, Reactions may not work for Office for Home and Business 2021, which is a perpetual license that does not include Exchange Online. Learn more about the differences between Microsoft 365 and Office 2021 in Office Support.
Reactions are also not currently supported with senders that are outside of your organization.
I hope this helps you understand the limitations of Reactions in Outlook. If you have any further questions, please feel free to ask.
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