MAPI error

I am running Exchange 5.5 sp4 and trying to send messages via Mapisend. I’ve placed the maipsend.exe and the batch file within the sys32 folder. I’ve tried the batch file and have had no success. I then manual try to send via command prompt w/the following lines:

c:\winnt\system32\mapisend -u “ms exchange settings” -p password -r sxxx-cxx@sxxx.axxx.mil -m “This is a test msg from HQ SXXX SXXX. If received, no action is required” -s “Hourly Mail Check”

I get the following error: ERROR: MAPI Logon Failed: 3

Can anyone advised as to why this is happening and what I can do to fix it?
Thanks!