IP Hacked - or not..?

[SassyK]

I sent an email to a good friend of mine at approximately 4.00 am Sunday Morning. Less than 12 hours later another friend contacted me and said he had been forwarded the email by the person I sent it to – it had his email address as the sender to prove it.. I thought this highly unlikely and asked the first person who insisted he had not sent or shown it to anyone else, in fact he had not been online since just after I sent him the email until an hour or so earlier.

I asked the second friend to send a copy of the received email to me in order for me to check the full header and determine the ip address of the sender, which he reluctantly (it seemed to me) did. When I checked the email header for the ip address from which it had been sent I found that it was the same as the one it had been forwarded to – the second friend! He pointed it out to me as soon as I received the copy and said this “anonymous” troublemaker was trying to make things even more upsetting.

However, since then I have been thinking about this. The fact that the full email and attachments were forwarded to someone else in the first place means that my email account must have been hacked into and the email taken from my sent file. This is the latest episode in a string of very unpleasant emails and fake pms. However what worries me most is the identical ip addresses and I need to know for definite if this is possible. I know that it is possible and fairly easy to change the email address to look as if it came from someone else, but I am unsure about changing one’s ip address in this way. Is it possible, if you have all the details, to change your ip address (maybe through manually configuring the TCP/IP) to make it look as if an email has been sent by someone else.

Grateful thanks in advance for your reply.

[Cellus]

Keep in mind that a forwarded e-mail's header will have the "second friend's" IP address because, quite frankly, he was the one who forwarded to you!

[SassyK]

Yes I am aware of that, however I am talking about the very first ip which is the one of the sender of this forwarded email and that matches his as the receiver - it was him who actually pointed it out to me when I received the copy - though I do not know whether he did that knowing that any second I was bound to remark on it.

I am just concened that the "anonymous troublemaker" and my friend, who is pressing for a more serious type of relationship, are one and the same...

[Cellus]

You can use something like SPF, SenderID, DomainKeys, etc. to verify the sender's location.

To really lay it out in detail, take a look at the Wiki on E-mail Authentication, specifically under the sub-section "Authenticating senders".