If you mean in your address book, sure can.
Go to your contact in the address book, press the menu key, select edit. Scroll down to Email and press the menu key and select Add Email Address.
The difference between stupidity and genius is that genius has its limits.
When you take things for granted, the things you are granted, get taken.
Even a mosquito doesn't get a pat on the back until it starts to work.
Too many people miss the silver lining because they're expecting gold.
[BES 5.0.3 / GroupWise 2012 HP2]