This is presented as true to the best recollection and is offered
for guidance with NO warranty expressed or implied.
Your mileage may vary.
If your E-Mail account can be managed over the InterNet from a Browser,
then anyone anywhere in the Universe with your password and InterNet access
can send out messages that appear to have come from you,
to everybody and anybody in the address book that you would use.
PREVENTION: Guarding your password can help.
Not keeping an address book on the Web can also help.
If your E-Mail server (e.g., AOL, Verizon, ATT, Earthlink, etc., etc.)
has some MalWare installed,
then anyone anywhere in the Universe with access to that MalWare
can send out messages that appear to have come from you
to everybody and anybody in the address book that you would use.
PREVENTION: Using only well-protected E-Mail services can help.
If your E-Mail Client (e.g. Outlook, Thunderbird, etc.)
has some MalWare installed (i.e. on your PC),
then anyone anywhere in the Universe with access to that MalWare
can send out messages that appear to have come from you
to everybody and anybody in the address book that you would use.
PREVENTION: Keeping your security shields UP and updating often can help.
If your PC is available to others at home or work or at the coffee shop,
then anyone with access to your PC
can send out messages that appear to have come from you
to everybody and anybody in the address book that you would use.
PREVENTION: Keeping the kids out of the office/den can help.
If you send a message to several people as noted in the "To:" or "Cc":" fields,
and any of the recipients' E-Mail clients happen to have some MalWare installed,
then anyone anywhere in the Universe with access to that MalWare
can send out messages that appear to have come from you
to everybody and anybody noted in your message or the recipient's address book.
PREVENTION: Using the "Bcc:" field to send to more than one person can help.
Choosing your friends carefully can also help.
If you use a wireless/WiFi connection for your PC, then anyone with sufficient
access to the connection can read all of the address (and text too) in
all of the messages that you send and receive and
can send out messages that appear to have come from you
to everybody and anybody noted in your messages.
PREVENTION: Using good encription whenever possible can help.
In ANY of these cases, the process of the interception of the addresses
can also send the needed addresses to its "home base"
anywhere on the InterNet, where it can be accumulated, stored, cross-indexed,
sorted, and used later for whatever malevolent intent it might have.
PREVENTION(partial): Using a good 2-way FireWall can help.
There are NO GUARANTEES that any communication is truly private.
The InterNet was designed to be used between "honorable peers".
There are plenty of DIShornorable people out there;
some like to toy in the area for fun and adventure;
some for personal gain;
some for the satisfaction of wreaking havoc on others.
KEEP YOUR SHIELDS UP AND YOUR HEAD DOWN.