.install file not working properly
If I had a penny for every time I've done this...

You've forgotten to return $schema from your email_form_schema() function.

You'll need to reinstall the module (not just disable then re-enable) for the changes to take effect.  

There's also a problem with the "last" column. It's a "varchar" and you're using the "unsigned" property which isn't compatible with that type.

You also need to provide the "length" property for all of the "varchar" type columns, including "first" and "last".