There is an option for users to have an alternative email and be allowed to choose for messages to be emailed to the place they prefer. The messaging settings in the site admin tools lets you enable the option "Notification email override". Once enabled, users can check their Notification preferences under their profiles and from that page their will be settings for the different modes of notifications. One column is for the email notifications. There is a little gear on that column. Clicking the gear will bring up a settings menu that lets the user set an alternate email for their notifications.