I have a dispute on my hands in which the other party (landlord's real estate agent) dishonestly claims to not have received an email that I truly did send.

My questions is, what are the ways to prove that the email was indeed sent?

Thus far, the methods that I have already thought of are:

• Screenshot of the mail in the outbox
• Forwarding a copy of the original email

I am aware of other things like HTTP/ SMTP headers etc that would exist as well.

• Are these useful for my purposes, and if so how do I extract these?

The email in question was sent using Yahoo webmail ( http://au.mail.yahoo.com/ ).

Edit: I am not seeking legal advice here, just technical advice as to how to gather this information.