I dated a man for nearly two years and we broke up exactly one year ago. He borrowed a total sum of 3,000 from me and now refuses to pay me back.

The emails are no guarantee that you will win, but they are helpful.  Even though they are not from him, they may constitute what are known as "adoptive admissions".  Sometimes when someone is accused of something which an innocent person would deny, and that person is silent, it can be considered as if the accused person had admitted what he was accused of (this is in civil cases, not in criminal matters where the accused has a constitutional right to remain silent).  For example, if, after an car accident, one driver accuses another of having run a red light, and the other does not deny it, that may be considered by a court to be an admission.  Of course, your ex may deny ever receiving the emails, or may claim that he did deny them, or that he paid you back after the emails were sent, or any number of things to try to demonstrate that these emails do not prove anything.  It may come down to a matter of who the judge believes.  It would be very helpful if you had some other evidence, such as a witness to one or more of the loans, or a canceled check showing the loan.