Hello Lim Zi Lin,
Thank you for reaching out to Microsoft Support!
We have tested the endpoint and it works well. We can receive the mail. Please check the aspects.
Log in to the email box that sends the invitation to check whether the email has been Sent, check it in Sent Items.
If the message has already been sent, check whether the invited user's mailbox has blocked the message or whether the message is classified as spam.
Share my test results:
Hope this helps.
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