Polyxarc is available on my BBS, comes with C source code,
works under MSDOS, OS/2 and AmigaDos, is public domain,
and will unarchive mail packets and then (if you want),
automatically delete the original archive if it was
successful.  I use it on my system, and you may find it
a preferable way to unzip your archives.  That then 
transfers the problem to getting pktjoin to display
error messages.  But you can probably use Paul Markham's
PKT sorter to do that for you, as it's got far more code
in it than PKTJOIN, and probably does full error checking.
That then transfers the problem to PKT2QWK.  But Bob is
writing a replacement for that, which will have full
error checking and no bugs.  That completes the cycle.
BFN.  Paul.
@EOT:

--- Mksmsg