Accept Input of many email addresses or mailing list

I was wondering about the best way to accept a large number of email addresses in a web application.

I am designing a system where one user will initiate a process by entering several hundred email addresses.

I would imagine there is a way to accept Outlook mailing lists as input, but I cannot seem to find any resources on this.

What I'm Looking For

• The easiest way (as a user) to enter several hundred email addresses, assuming the user already has the desired emails saved in a mailing list.