Your problem is that PROBE1 and PROBE2 are not separate text files.
PROBE1 and PROBE2 are part of DEFAULT MAILTPL (and thus, if you change
them for a specific list, they should be part of your listname MAILTPL).
Please see chapter 9 of the list owner's manual (chapter 10 of the
site manager's manual) for information on how to create a mail template
file for your list (in your case, iaolist-l.mailtpl).

Nathan