How do I stop My S-9 from multiple notifications for every e-mail?

First, this is not about a notification repeat where the notification repeats on a regular interval until the new message is read or acknowledged. This is about my phone blowing up with multiple notification tones every time I receive an e-mail on Outlook. When an e-mail comes in I get the notification time 5 or six times in a row, one right after the other. Can't figure out how to get just a single tone

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