Schedule a meeting

Dear @Penny Hoh, 

Thank you for posting your question in the Microsoft Q&A forum.   

May I ask what domain those external users are using? Are they users from another business tenant, or are they using domains like @gmail.com or @outlook.com? Please help me provide a bit more information. 

If they are users from another tenant, it's possible their IT department is blocking emails from unknown domains. Also, please ask those external users to check their Junk/Spam folders to see if the email is there. 

Alternatively, the cause might lie within your own organization's policies, for example: 

• Blocking external access. 
• Outbound email filtering policies. 

To verify if there is actually a blocking policy in place, please open that meeting in Outlook, select Forward this event > enter the external email addresses > Send. Then, check if they receive that email. If they still don't get it, a blocking policy is likely the cause. 

In this case, you should right-click the meeting link and select Copy Link, then use a third-party app or your personal email account to send that link to them. 

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i send the invitations email to my colleague using company domain and at the same time send to yahoo.com too but both did not received my email invitation.