parked domains does not have username / password, only addon domains and account domain can have password, could you specify which one you are trying to modify?
My situation is :
I have an account with domain [my_main_domain.com] which works normally.
Today I added another domain [my_parked_domain.com] to the above account as parked domain, everthing is fine until it happens that I need an E-mail address like [[email protected]
_parked_domain.com], I were able to create the E-mail address [[email protected]
_parked_domain.com], even modify its quota using cPanel API.
But one thing doesn't work through API call : I'm unable to change the password for the E-mail address [[email protected]
_parked_domain.com] using API, "email::passwdpop" doesn't work with E-mail of a parked domain, it only works for the main domain.
However I can change the password of any E-mail accounts, be it main domain or parked domain by using cPanel interface as usual, so I think that something is wrong here.