Or another approach would be to have this column of XML data type. A single value can store an unlimited (reasonably) number of email addresses. The XML structure can also store -- in attributes and tags -- some other data relevant to the email addresses.

 < Addresses >
     < Address value="address1@mydomain.com" Type="Office" IsDefault="True">
     < Address value="address2@mydomain.com" Type="Home">
     < Address value="address3@mydomain.com">
...
 </ Addresses >

The choice is to be made depending on how many of email addresses the database will store eventually, and on how fast/frequent the access to an individual email address is expected to be.