Can't Change Profile Email: Upper/Lower Case to Lower Case

I have noticed a minor bug in Groupsite profile settings (My Settings, My Profile, Professional Contact, Email).

If you create an initial email using both upper and lower case letters, for example Foo.Foo@FooBar.com

then later want to change it to all lower case letters like foo.foo@foobar.com

It appears you cannot.  Even if you add another temporary email address, delete the upper and lower case email address you want to change (Foo.Foo@FooBar.com), then create a new email address with all lower case letters (foo.foo@foobar.com), Groupsite remembers the email address you already used with the upper and lower case letters and "automatically" uses this again, even though you reentered it with all lower case letters.

I have tried every possible way I can think of to "trick" Groupsite, but it will not let me reset my email to the all lower case letters version!