Dear #Kunjan

I hope you are doing well.
I can only thank you for your valuable advice.

You are a unique and special person in the world of IT.

This time, I solved the problem again.

Dear Kunjan

I hope you are doing well.
I can only thank you for your valuable advice.

You are a unique and special person in the world of IT.

This time, I solved the problem again.

Hello Fronzies,
I hope you are doing well

Notes aren't deleted - they're hidden. The mail.mt_note subtype is internal=True, so portal/non-employee users can't see them. 
Fix: Assign the user to the Internal User group (base.group_user) 

I hope this information helps you

Thanks & Regards,
Kunjan Patel