In Outlook 2007 you wouldn't find a Contact Group because it's called a Distribution List in this version of Outlook, for more details see How to import a Distribution List sent you as an attachment.
You can easily share you distribution lists by attaching them to e-mail. There are two ways of attaching distribution list: drag-and-drop and the Attach Item command.
It is a pretty time consuming task to send message to multiple recipients at once. Fortunately, if you regularly send e-mails to the group of people, you can create a distribution list and send them an e-mail with just a few clicks.
You can use the Send/Receive Settings to specify a limit on message size for messages downloaded in the Inbox.
Sometimes it is to your advantage to not download an entire e-mail from your mail server, such as when you have a slow Internet connection or you want to start looking through many e-mail messages for a particular one as soon as possible. Outlook offers the capability to download only the e-mail header, which includes the sender and the subject of the e-mail, and display these onscreen before downloading the message itself.
Suppose you will be out of the office and want to alert anyone who sends you an e-mail of that fact so they'll know when they can expect you to respond. In that case, you can set up Outlook to send an auto-reply to anyone who sends you a message.
If you frequently sign your messages using not only your name, but also additional information such as your job title and contact information, you'll appreciate Outlook's Signature feature. When enabled, it appends text of your choice to the end of every message that create and/or reply to.
When you need as much space as possible on screen to view a message, you can collapse (or minimize) the Ribbon to only its labels by double-clicking the label of the tab you're currently using.