Candidate not receiving Interview schedule Notification email

Summary:

Content (please ensure you mask any confidential information):

We have enabled MS Outlook 365 integration and Teams integration with Interview schedule.

Interview schedule Notification is active.

When we schedule an interview with a candidate and save, The Interviewer, Organizer are receiving the interview schedule email. But Candidate is not receiving Interview schedule Notification email in the candidate email id defined for the candidate.

Kindly let us know, What could be causing this issue.

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This is an external candidate.

Candidate Type - External

Candidate Preferred communication is Email

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Candidate received the verification pin email during job apply in career site.

sent an email from Messages section of the requisition and candidate received the email.