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Regarding to your description, I would recommend setting the follow-up after sending the email with Microsoft To do app in New Outlook, please try the below steps:
- Compose your email as usual.
- In the Sent items folder, flag the email to follow up
- Select To do on the left pane
- Select Flagged emails, drag the email to tasks pane
- Set due date and remind option
If you have any further questions and concerns, please let us know. Looking forward to your response.
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