There are many applications useful for sending emails. Here are a few and their uses in no particular order.
MICROSOFT OUTLOOK - Allows you to send and receive emails, add and maintain contacts, and schedule appointments. It has a notes portion and also a todo list. Cost - around $5.00/month
GMAIL.COM - Allows you to send and receive emails, add and maintain contacts. Cost - Free to use
MOZILLA THUNDERBIRD - Allows you to send and receive emails, add and maintain contacts. It includes a chat feature. Cost - Free to use
APPLE MAIL - Allows you to send and receive emails. You can add and maintain contacts with another contact list. Cost - Free to use
WINDOWS MAIL - Allows you send and receive emails. You can add and maintain contacts. Cost - Free to use