Receiving emails on Zmail but cannot send any out

When I am preparing an email and I include an addressee, the spinning wheel turns on and never goes away. When I hit send I get "Cannot send email (Error code 103, 10004)"

I cannot find any references to those error codes in the help information. It is definitely not an Internet connection issue and I've had no difficulties sending and receiving to all my other email accounts. Is this a configuration error? If so, I am unsure where in the mail settings I need to make changes. Thanks!