No service provider, MSN or anyon else, will send you an email asking you to verify your social security number or password. If you're not sure, call or email MSN yourself using contact info from the MSN site's contact information. Don't trust any contact information given in that email you received, and don't trust a website you get to via a link in that email. I promise this email is not from MSN.

Don't provide anyone your social security number unless necessary -- for an employer's tax paperwork, for example. Anyone who has your SSN might as well have open access to your wallet.