What do the Status numbers in the DomainServices table of PSA mean?

[slackticus]

I am trying to write a query that will show me a count of the active email boxes by domain. Some domains do not have web hosting enabled, but do have email.

Here is what I have so far:

SELECT domains.displayName, mail.postbox, COUNT(domains.id) as count
FROM domains, mail, DomainServices
WHERE domains.id = mail.dom_id
AND domains.id = DomainServices.dom_id
AND mail.postbox = 'true'
AND DomainServices.type = 'mail'
AND DomainServices.status ='0'
GROUP BY (domains.id);

The line that I want to verify is right (and better understand) is the

DomainServices.status ='0'

I see that when I turn off mail for a domain that DomainServices.status ='16'
and when I turn it back on DomainServices.status ='0' but what do the other status numbers mean? Is 0 the only status for active email services?

If anyone knows, I would appreciate the help.