Use sa-learn to teach spamassassin what is spam

For a couple of years now I have been using Spamassassin with great success. Over time I occasionally would teach Spamassassin what spam is with the 'sa-learn --spam mboxdata' command. It has been awhile since I did this and figured it was time once again to teach Spamassassin a thing or two about spam. Locally I use only Apple for my computers, and for my software, but this will work equally from Windows machines. My servers all run RHEL4. For a couple of weeks I collected any spam that got through to me, into a folder I call SPAM. Then when I think there is enough spam in the folder--in this case 487 spam--I export the SPAM folder into an mbox format file. On Apple this is easily done using this hint from MacOSXHints. Windows users I am not sure about, but a quick search on Google should reveal some results. Next we FTP our mbox folder to the server. Then we simply run:
sa_learn --mbox --spam mboxdata
Replace 'mboxdata' with the name of the file you uploaded. You should see a message that looks similar to this:
Learned from 473 message(s) (487 message(s) examined).
My reason for posting this is that I forgot to add the --mbox flag and simply got a message that looked like this:
Learned from 0 message(s) (0 message(s) examined).
Have fun with it. Let me know if you see anything I missed.