Two e-mail addresses from same computer?

Had a discussion in the pub the other evening about someone having 2 e-mail addresses from the same computer. The question is : would it be possible for someone who gets e-mail communication from both addresses to find out its the same computer ?

rabbit said:

Had a discussion in the pub the other evening about someone having 2 e-mail addresses from the same computer. The question is : would it be possible for someone who gets e-mail communication from both addresses to find out its the same computer ?

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I'm guessing if they went to the trouble of trying to find out then the sender's IP address might identify them. Calling computer experts: if you send emails from different accounts but on the same computer won't they have the same IP address?

rabbit said:

Had a discussion in the pub the other evening about someone having 2 e-mail addresses from the same computer. The question is : would it be possible for someone who gets e-mail communication from both addresses to find out its the same computer ?

Click to expand...

short answer: yes

How does a person go about finding out the the sender's IP address ?

If the sender knows what they are doing, it is often not possible to find where the email is originating.

SMTP headers are easily forged, and open relays are often used.

In general:

You have two e-mail accounts setup on your computer. You send two e-mails to me, one per account.

If I look at the "headers" of the e-mail (in Outlook it's normally something like open the e-mail and then click view/options.) In there I'll see things like the IP but (and this is the bit I'm interested in) if you've named your computer something, the name of your computer will be in there. This is how I differentiate between who sent the e-mail (for example, two computers attached to the same network will both use the same IP as the firewall/router/etc) but will have a different computer name.

Know what I mean?

PS Sorry for the terrible grammar in this post, I'm a tad hungover...