IP Address / Computer ID Questions (6)

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People…

When I e-mail my office computer at work, from home…If I check out the e-mail’s properties on the Details tab…it tells me the message was “Received From”: 1) a unique ID c/o letters & numbers (e.g., bubba9axb7yui4bt); & 2) a 12 digit number (looking similar to 123.456.789.123). I am assuming the first is my Computer ID; & the second my IP Address.

If I then go to my web mail service (in this case, yahoo), send an e-mail back to my home computer; & check out that e-mail’s properties…in that message source, the very last “Received From” listing also shows my home machine’s IP address.

So…a few questions:

1) That first ID…that is in fact my Computer ID, unique to only my machine, right?…& where do I find that ID’s location/information on my hard drive?

2) The second number…that is in fact my IP Address, right? Is that number unique to my machine, or is it a number assigned by my ISP (meaning…does it change if I change internet service providers?)

3) How in the heck did yahoo know my web mail message originated from my computer? Does their e-mail utility do a search of the user’s hard drive to locate that number in a specific file & folder…or do they get it from the home e-mail address one provides when they sign up?

Thanks,

mark4man

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I don’t know about the first ID, but the second one is indeed your IP address. This address is assigned by your ISP. In the days of dial-up connections, this IP address was often dynamic, i.e. you got assigned a different IP address each time you dialled in; with cable and (A)DSL, you are usually assigned a fixed IP address for an extended period of time.

When you send an e-mail, your IP address is included in the mail “envelope”; as the mail gets relayed through different servers on its way to its destination, more IP addresses get added to the “envelope”.

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One place to check your public IP address (the one that your router or DSL modem or cable modem puts in your outbound packets so responses can come back to you) is http://www.ipchicken.com[/url%5D. It’s also on this test page http://carbocoma.com/db_tut/svrvars.asp%5B/url%5D. If you check that from home, I think you will find that this will only be the same address as in your Yahoo! email “Received” headers if you sent the Yahoo! email from your home PC. It is not associated with your account, but with the machine logged in to Yahoo! when sending mail.

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Thanks, guys…

Can always count on Hans & jscher !!!

mark4man

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