If you need to make sure your password is working for a particular domain, try running a program as that domain\username.

1. Right-click on the short-cut and choose 'Run As...'
2. Change the radio button to 'The following user:'
3. Enter the domain\username & password.

If the app runs, your auth pair works.

Note: If you need to enable 'Run As' on your system, this Microsoft article will be helpful.

Use these queries to change the structure of a DOMAIN constraint:

ALTER DOMAIN foo DROP CONSTRAINT bar;
ALTER DOMAIN foo ADD CONSTRAINT bar CHECK (VALUE = 'baz'::text);