Thunderbird Setup
Checking your email
Thunderbird will automatically check for new email messages every so oftern. The frequency of this can be changed by choosing Edit > Account Settings... from the menu bar and then choosing Server Settings .
Selecting the Get new messages (shown below) forces thunderbird to check for new messages.

Sending email
Select the Create new message button from the toolbar - this is below Edit. A new window will open allowing you to type your message.
You can also select File > New > Message from the menu bar, or use the keyboard shortcut Ctrl/M to compose a new message.
Address book
Thunderbird can search the central directory for email addresses. If you would rather search just people in DAMTP, rather than the whole university then add (InstID=DAMTP) to the Search filter - this is found under the Advanced tab when entering the University Directory (ldap) server details.