If you want to send one email to several people create a new entry in your address book. Enter one nick name (such as jokes) and then enter each email address separated with a coma (,)
Now when you need to send to these people, just type in that nick name.
If you are doing an on going mailing each day or week with a list of more than 20 addresses, you need to look into software that will do the job for you. You may need to set up a special email just for this. LetterRip, MailMan, directMail maybe worth looking into.