The ability to create Contact Groups is probably one of my favorite features. If you are on a committee or work within a department, or just generally have a specific group of people to whom you regularly send emails, then you should be using Contact Groups in Outlook (or Google).
Using contact groups will make sure that everyone in your department or committee gets the same email and that you’re not needing to think about who your committee members are.
This feature saves you having to count the number of recipients, and obliviates that deer in the headlights look when you mention an email you distributed.
The only caveat is that you do have to keep your group updated when people join or leave your department, but those changes are hopefully few and far between, and given how many emails you send out on a regular basis, a very small burden to bear.