TAPI Error Values

TAPIERR_INVALDESTADDRESS
The pointer to the destination address is not valid, is NULL, or the destination address string is too long.
TAPIERR_INVALPOINTER
The pointer does not reference a valid memory location. One or more of the pointers lpszDestAddress, lpszAppName, lpszCalledParty, or lpszComment have been specified but are invalid.
TAPIERR_NOREQUESTRECIPIENT
No recipient application is available to handle the request. The user should start the recipient application and try again.
TAPIERR_REQUESTFAILED
The request failed for unspecified reasons.
TAPIERR_REQUESTQUEUEFULL
A recipient application is active, but the request queue is full or there is insufficient memory to expand the queue. The application can try again later.

Any other TAPIERR_ values are nonfunctional in Win32-based applications and must not be used.