browse to url mail.billing.foo.com.au returns boxbilling error for this subdomain as well as mail.whmcs.foo.com.au. Is normal?

Hi guys,
I am really confused. First i would just like to say, i do not have any mail client installed…so im not expecting that the following urls should work. However, the error i am getting is not what i expected.

I have two virtual servers on a webmin machine…
whmcs.foo.com.au (whm complete system)
billing.foo.com.au (box billing)

I am having problems with a problematic install of Box Billing to billing.foo.com.au, ie… it will not install properly as it “cannot connect to database” during setup, is producing an error on what i thought is a different url…ie mail.whmcs.foo.com.au. I have checked my database credentials repeatedly, even tried new database and new user without success.

Anyway, is the following url issue normal behaviour with a subdomain on virtualmin?

Typing in the following urls, mail.billing.foo.com.au and mail.whmcs.foo.com.au, both produce an identical box billing generated and logo page errors (box billing is not installed on both subdomains???)

BoxBilling
Code: 1698

SQLSTATE[HY000] [1698] Access denied for user ‘foo’@‘localhost’

i have checked my whmcs@whmcs.foo.com.au webmail in webmin>postfix>User Email and the postfix email service is sending and receiving emails and appears to remain unaffected which is good. However, i do not understand the meaning of the above error message, or why it is being generated on what should be different virtual server urls with the same box billing logo?