Email address in Mail & Messaging section of the contact doesn't match correct email address

I have a single email address [.gmail] I loaded for a contact that begins with a captial 'I" but when I tried sending it I got an error. I looked at the contact info I loaded and under "Mail & Messaging" the address appears in light blue and first letter of the address begins with a small 'i'. Thus, I get an error and message doesn't go out. I can't change the email address under "Mail & Messaging". What's next? Thanks...