I looked at his sent items but it shows Friday's date. I need to prove that he made the system date time to send me a mail on Monday.
Both of us were using Windows 7 32 bit operating systems. The email headers will show the timestamp of the message when it was handled by each mail server, very likely this will include your correspondent's
Backdating emails outlook server his ISP's server and your server one or more of your ISP's servers.
To access the email headers in your copy of Outlook read this guide. The header of the email could give you that information, as each mail server the message passes through adds the time based on the server's clock that the message was received on that leg of the journey to your machine. If you can't see full header of the email, here are directions for finding this setting in all versions of Outlook. Microsoft has a breakdown of how to read their Outlook headers here.
How to prove when the email
Backdating emails outlook sent? BlueBerry - Vignesh 5, 20 50 Do you have access to the email logs?
I mean, on the server. If you your company is hosting it's own smtp server then you can get access to the logs.