There are several different operations you can perform on an E-Mail.
After you have completed writing an email, you can send it by click the Send button. You can also send saved emails.
Check your email accounts for incoming emails. You can setup a regular time to check for new emails under Tools -> Setting -> General -> Send/Receive
You can also click Send and Receive All in the mail toolbar or click on Tools -> Send and Receive to send all your outgoing emails and check for incoming emails at the same time.
Reply an incoming email by selecting it in the main panel and clicking Reply in the mail toolbar or select Actions -> Reply...
You can forward an email by selecting it in the email list and clicking Forward in the mail toolbar or select Actions -> Forward...
Manually mark an email you haven't opened as read by Right-Clicking it and select Mark as read.
Manually mark an email you have already opened as Unread (perhaps to remind yourself to read more carefully later) by Right-Clicking it and select Mark as unread.
Move to folder...
You can move your emails to another folder by Right-clicking the selected email(s) and select Move the folder.
In the mini-explorer that popup, select an existing folder or create a new one to which you wish your email(s) to be moved to.
Same as move to folder, except a copy of the selected email(s) will also be kept in the original folder.
You can delete an email by Right-clicking it and select Delete, or simply press the Delete button on your keyboard.
Opens a window with the header of the selected email.
Opens a window containing the source of the selected email.