It is not covered well in any of the manuals I've read, but thankfully, I found this 
tidbit in a message board going back to 1999.

If you set up your "reject.sys" file to "Hold" incoming messages for review, 
you will be informed by FBB (as Sysop), that you have held messages.

In order to disposition them, you must use the 
RE command.

This command will display each message, one at a time, and give you several 
options, as follows:

(A) rchive, (K)ill, (L)ocal, (Q)uit, (R)ead, (V)erbose, (U)nhold, (CR)finished ?

If you select U, the message will be posted on the BBS. Obviously if you select
K, it will delete that message and move to the next.