I suggest reading the rules. It's to prevent people from cheating.
"1/ Multi Accounts
Every member of the combine may only have ONE character. Registering more than one character, logging into someone else's account or giving your character to someone else in order to create a new one is PROHIBITED. Anyone breaking this rule will be banned from the Combine.
Free e-mail addresses may not be used for joining the Star Wars Combine. Instead we allow ISP, school, some work, and other paid e-mail addresses, and if you own a private domain you must use email@example.com or firstname.lastname@example.org.
If you are sharing your computer or internet connection with other persons that are also members of the Combine, you must register all accounts by sending the handles to register to email@example.com - this includes handles and the email addresses of all players using the computer. Players who are sharing a connection must all be members of the same faction or one or all may be freelancers.
Explanations such as "I don't have more than one character! The second one belongs to my sister!!" will not be accepted.
Players banned as a result of the multi-rules who request an unban may be subject to a partial removal of credits, assets and/or XP, to be determined on a case-by-case basis upon their return to the community. This punishment is fully supported by the administration and multi-accounts staff and may not be disputed as it is a condition of being unbanned."
You only need the non-free e-mail for registration. After that you can set your hotmail e-mail address as your preferred e-mail in your account settings and your original registered e-mail won't be used for anything again.
IPs are also not always the best option, particularly in cases of dynamic IP addresses (as most dial-up ISPs use) and larger ISPs where multiple users tend to show up on the same IP address despite being complete strangers.
We use a number of different methods to ensure that players do not register multiple accounts, and this is just one of them. For a time, free e-mails were permitted, so it is not as though that has never been tested. (: