mail::account::hasCapability — Mail account's properties
        mail::account *account;
| bool
            flag=account->hasCapability( | std::string capability ); | 
This function checks this mail::account's properties. The list of potential properties, or capabilities, depends on the account. The currently defined list of properties are:
LIBMAIL_SINGLEFOLDERWhether this account contains a single incoming mail
            folder (currently only pop3 accounts have this capability
            defined).