Hmmm, maybe something like this...
if(String::getSubStr(%msg, 0,13) == "You received " && $AutoDropOn == 1)
Drop(%msg);
Note1): Drop(%msg) will be your autoDrop function, where it goes through the list of all the items you want to drop, and drops them.
Note2): $AutoDropOn is there, so you can bind a key later to toggle it.
Hersh