one of the documented procedures in this installation of the ACS
bulkmail_key_code   bulkmail_id   user_id
What it does:
Creates a bulkmail key code, which is of the format ABC
Defined in: /web/philip/tcl/bulkmail-utils.tcl

Source code:

    append output $bulkmail_id "A" $user_id "B" [ns_time]

    # For good measure, we'll calculate the checksum after making the letters
    # lowercase.  This could confuse the stupid attacker who's trying to
    # figure out what that number is.  Not much else.  We have to be sure
    # to do this when decoding, too.
    append output "C" [bulkmail_simple_checksum [string tolower $output]]

    return $output