It is a requirement for members to verify their email addresses in order to access their accounts in game. A valid email address is necessary for account security and id/password retrieval.
If you have not received an activation email:
1) Check your spam and junk folder on your email providers website, some providers have BOTH a spam and a junk folder
2) Check that your email address is correct, you can change the email address with a valid password
3) Request your activation email again, emails are sent immediately
If you receive email through a software client such as Outlook using pop3, you may need to log into the website of your provider (virginmedia.com for example) in order to view the junk and spam folders