Hi Ravi,
When you fill document field of the email in the flow, not directly using document value from note, you need use base64ToBinary() to convert document.
Please refer following steps.
1.Add ‘Compose’ step before ‘send email’ step.

2.’Send email’ step.

The following screenshot shows full flow:

Regards,
Leah Ju
Please mark as verified if the answer is helpful. Welcome to join hot discussions in Dynamics 365 Forums.