Acoworker is concerned about the veracity of a claim because the sender of an email denies sending it. the coworker wants a way to prove the authenticity of an email. which would you recommend?

Some recommend way to prove the authenticity of an email:

The coworker as truthful to the company or organization he or she has to check where the same mail is sent long back to the same sender.If search on emails sent item if he sends it will be well and good. Some time backup the mail will be help to proven authenticity of an email. Sometimes once mail is downloaded into ms-outlook or lotus domino some time mail persists in the mail server.He or she can coordinate with the mail server administrator to possible get a log file of sending mail and he can proceed as a record to management.

Smiling is a best one of business