What version of avast do you have, the latest being 6.0.1091 ?
If you registered from the Register Now button (see image) in the avastUI, Maintenance, Registration, you should have been able to do that directly without the need to get an email ?
Only if you used the Offline registration, Registration form button, would you receive an email with your registration key which you would have to input. Using the previous method all this is done within the avast interface no need to file in the forms, wait for an email and insert the key.