Cannot send email invites to email addresses starting with a capitol letter?

Description:

I have a hunch that your email invite system will not accept email addresses beginning with a capital letter.

Not being tech savy, I opt to use "Invite via Email" option. I cannot send an email invite to an email address (which starts with a capitol letter) which I know to be valid.

Repro Steps:
1. Sign into BK with your account
2. Select "Friends"
3. Mouse click on "Discover & Invite Friends" button
4. Mouse click on the "Invite via Email" tab
5. In the "Your friend's email" input box, type in an email address starting with capitol letter
6. Mouse click on "Send Invite"

Result: Sending an individual email invite to an email address which starts with a capitol letter seems to always give an error message

Expected: User should always be able to send invites to email addresses which start with capitol letters