Twitter does not allow users to create multiple accounts using one email address. Normally, it should not be a concern, but occasionally one might need more than one Twitter accounts. For example, one Twitter handle for personal tweets and the other for giving automated updates about a website or blog.
If you have a Gmail account (Who hasn’t!), you can register multiple Twitter accounts with single email address, using a simple hack.
All Gmail addresses are assigned an alternative Googlemail email address as well; if your Gmail address is firstname.lastname@example.org, you receive email as email@example.com as well.
Need some more alternative addresses! Gmail does not recognize dots (.) in email addresses. For Gmail, firstname.lastname@example.org is same as email@example.com or firstname.lastname@example.org or paper..email@example.com. Make as many combinations as you want and use them for creating multiple Twitter accounts.