Doug
Hi toruser
Yes, it is possible to determine the sender's original IP from the Header Information of an email.
Have a look here at this introductory level information:
http://www.johnru.com/active-whois/trace-email.html
There are dozens of legitimate reasons why people wish to cause their internet identity to be anonymous.
And some folks want to remain anonymous based on a personally held gut-level reason.
Alternatively, there are dozens of legitimate reason for a person to want their identity to be relatively public.
IP identity has some "real-world" corollaries such as the Return Address you put on the outside of a payment envelope, a home or business phone number or a cell phone number.
The double-edged nature of identity vs. anonymity is that most often the person will want "some" folks to be able to reach them, and may want "others" to not be able to reach them. The more people you want to have the ability to reach you, the more likely your identity can be deliberately or accidentally disclosed to those you wish to be protected from.
It's a true fact of life in these high-tech times, that the most frequently used method to obtain information about an individual, is the garbage can. People throw away receipts, billing information, check stub and ATM receipt copies, as well as envelopes and more individual information without shredding the paper first. And over a period of years, it is unlikely that very many of us at all, have observed garbage can security consistently. Any one throw-away item may not contain sufficient information to compromise a persons identity, but a collection of several items probably will.
Additionally, we voluntarily "give" our personal information to a variety of people, businesses, and entities, without truly understanding what may happen to our information after it is given. Have you ever received an email from a friend that was also cc'd to other people or forwarded from one friend to another? All of those addresses are now in the Header of the email, and your address is available to all of those people. If you've ever sent or received an item that offers a "tracking code" option, then you've given away plenty of information. If you've purchased or subscribed to a downloadable application or utility and check-marked the item that offers "send me updates about this product", you may have given away plenty of information. If you've recently applied for or received a credit card account, isn't it interesting that all of a sudden your mailbox is filled with offers for other credit cards. If you've recently enrolled or graduated from college, isn't it interesting that you suddenly start receiving offers for credit, loans, housing, products, vacations, job search services, and the like. Buying a car or major appliance may result in a similar flood of new offers.
In the physical world it is possible to obtain a Post Office Box to receive mail, so that routine communications do not receive a home or business address. However, many of the businesses one has to correspond with also require a physical address to be given inside of their database. You can receive a utility or phone bill at a Post Office Box, but the electric or phone company still needs to know the physical address to supply the service.
In the digital world, many savvy folks maintain more than one email account, sometimes called "throw-away" accounts. Such accounts can be used for specific purposes, such as registering software, business only, personal only, etc. This use of multiple accounts can limit the amount of spam email one receives, or limit most spam to only one account.
However, the user's specific IP is still available in all of these accounts, so identity is still available to a determined investigator.
Using 'anonymyzers" like Tor can provide specific protections during any specific internet correspondence, but if the user is concerned about privacy, it is well to consider the above kinds of personal information sources as well.
As to "configuring your machine, firewall, and router" to use Tor, it appears that the Tor sites offered by a google search or directly from the sites linked by Abydos, above will give you most of the information you need. Specific questions about problems using Tor may be best addressed in their Tor user forums. I'm not trying to discourage you from further posting of Tor related questions here in these forums, rather I'm being realistic about where you may get the most up to date information.
Best Regards
Yes, it is possible to determine the sender's original IP from the Header Information of an email.
Have a look here at this introductory level information:
http://www.johnru.com/active-whois/trace-email.html
There are dozens of legitimate reasons why people wish to cause their internet identity to be anonymous.
And some folks want to remain anonymous based on a personally held gut-level reason.
Alternatively, there are dozens of legitimate reason for a person to want their identity to be relatively public.
IP identity has some "real-world" corollaries such as the Return Address you put on the outside of a payment envelope, a home or business phone number or a cell phone number.
The double-edged nature of identity vs. anonymity is that most often the person will want "some" folks to be able to reach them, and may want "others" to not be able to reach them. The more people you want to have the ability to reach you, the more likely your identity can be deliberately or accidentally disclosed to those you wish to be protected from.
It's a true fact of life in these high-tech times, that the most frequently used method to obtain information about an individual, is the garbage can. People throw away receipts, billing information, check stub and ATM receipt copies, as well as envelopes and more individual information without shredding the paper first. And over a period of years, it is unlikely that very many of us at all, have observed garbage can security consistently. Any one throw-away item may not contain sufficient information to compromise a persons identity, but a collection of several items probably will.
Additionally, we voluntarily "give" our personal information to a variety of people, businesses, and entities, without truly understanding what may happen to our information after it is given. Have you ever received an email from a friend that was also cc'd to other people or forwarded from one friend to another? All of those addresses are now in the Header of the email, and your address is available to all of those people. If you've ever sent or received an item that offers a "tracking code" option, then you've given away plenty of information. If you've purchased or subscribed to a downloadable application or utility and check-marked the item that offers "send me updates about this product", you may have given away plenty of information. If you've recently applied for or received a credit card account, isn't it interesting that all of a sudden your mailbox is filled with offers for other credit cards. If you've recently enrolled or graduated from college, isn't it interesting that you suddenly start receiving offers for credit, loans, housing, products, vacations, job search services, and the like. Buying a car or major appliance may result in a similar flood of new offers.
In the physical world it is possible to obtain a Post Office Box to receive mail, so that routine communications do not receive a home or business address. However, many of the businesses one has to correspond with also require a physical address to be given inside of their database. You can receive a utility or phone bill at a Post Office Box, but the electric or phone company still needs to know the physical address to supply the service.
In the digital world, many savvy folks maintain more than one email account, sometimes called "throw-away" accounts. Such accounts can be used for specific purposes, such as registering software, business only, personal only, etc. This use of multiple accounts can limit the amount of spam email one receives, or limit most spam to only one account.
However, the user's specific IP is still available in all of these accounts, so identity is still available to a determined investigator.
Using 'anonymyzers" like Tor can provide specific protections during any specific internet correspondence, but if the user is concerned about privacy, it is well to consider the above kinds of personal information sources as well.
As to "configuring your machine, firewall, and router" to use Tor, it appears that the Tor sites offered by a google search or directly from the sites linked by Abydos, above will give you most of the information you need. Specific questions about problems using Tor may be best addressed in their Tor user forums. I'm not trying to discourage you from further posting of Tor related questions here in these forums, rather I'm being realistic about where you may get the most up to date information.
Best Regards
Kind regards Abydos 
