Change email address that Requests For Access get send to
Whenever a user tries to access a page that he doesn’t have access to he get’s the following screen:

At the bottom of the screen he can Request access. When he click’s the Request Access link he can enter a message that get’s emailed.
But where can you find/change the email address that get’s used to send these requests to?
When you are on a site, go to Site Settings and choose Advanced Permissions, click on the menu Settings and choose Access Requests. This will give you the email address used for requests from within that site. Since you can grant access at Library and Item level, these Libraries and Items will inherit the setting from the site that they are on. You are not allowed to change the email address at those sub levels, but you can disable the feature on them (i.e. for a whole library disable the Request Access feature).
