I have two year records of emails from two different yahoo IDs, one of which is someone whom I know.The other email was used to cheat some money out of me. When I checked the IP from the mails over the years they match. Though they have changed three times over the years, each time they changed, they both changed to the same IP at the same time. Is this enough proof that its the same guy? The last mail from the cheater ID was in march2011.The other mail ID from which I still receive mails from, has the same IP address as the cheater ID had in March2011.
I would say yes. Presuming your are looking at the correct IP address.
There a few IP addresses you can see in email headers. These include:
Your IP address
Their IP address
Your mail servers IP address
Their mail servers IP address
So just make sure you are viewing the correct one before you make any claims. But if you are 100% sure, then yes, it will likely be the same person, unless it’s two different people who are using the same office network with the same public IP address.
What you could possibly do, is to reply to one of the cheating emails and send it to the person who you think it is. They might be clueless on which email address they are using to reply from, or they might stop because they know you are onto them.