Let's say you put your club on the web: it's at example.com. You might want people to email the club officers, and they should have permanent email addresses like this: president@example.com, treasurer@example.com, etc. The people occupying these positions might change, but the names of the positions and their email addresses should not. When you get elected president of the Example club, email to president@example.com should just go to you without you needing to do anything besides telling us who the new president is.
This is why we use email forwarding to handle your email. The members of your club or organization probably have their own ISPs and email setups, and they won't have to change anything. We handle your web presence, we are not your internet service provider. However, if you do need us to handle your mail delivery (for example if you have no existing email address) we can do that, too, for a small setup fee.