Very small organizations can use names like Joe, or Mary or even Boss. Usernames become part of the address of an email system and are the calling cards of the internet. The same rules apply for passwords as for usernames with respect to what letters and numbers can be used. Much like you wouldn't want anyone rifling through your mail box at home, let alone reading your mail, email security relies on certain trust principals. Inside the envelope, the contents are strictly for you to open and read.
Email is very much the same way.
Though there are many ways to violate these trusts, using them ensures that system rules put in place on servers and other components of the internet will help protect your privacy. Your password is your front door key and mailbox key combined. This is the tricky part. This means a somewhat more complicated task than a PIN number but a slightly less complicated task than your home phone number plus your calling card number. Many organizations recommend a combination of alpha characters, numeric characters and a somewhat random arrangement.