mmm not really, you can, but the implications are that any email sent out will use this email address. Currently, AFAIK, you cannot differentiate email addresses for different purposes in Moodle. There may be a way, someone at the OU may have done it, yet not released it for general use, but for most of us, the only way to do it is to either use a dummy email address at install/setup or enter the database with something like phpMyAdmin, go to the Users table, "mdl_User" is the default, and manually edit the AdminUser's email. That will solve your immediate problem, but is likely to cause other problems.
As an aside, this is not something I have considered before. However, it does raise a number of interesting questions about how we might be able to use Moodle in the future. Think about placing this on Moodle Tracker as a new feature. Initially it would mean the creation of different automatic accounts, like AdminUser, specifically related to enrollment greetings, but perhaps editable fields in settings.