I got this reply from support yesterday:
In regards to your cert advisory
ca-2003-07 (
http://sunsolve.sun.com/pub-cgi/retrieve.pl?doc=fsalert%2F51181&zone_32=ca- 2003-07)
this does not affect the iplanet Messenger Server mail client. This only affects solaris boxes that are running the sendmail that is installed with the O.S. I have double checked on this. I have talked to upper level techs
about this and the iMs 5.2 is not affected by this.
I realize the MTA code is different from sendmail's, but the exploit (or some variation of it) might still work on the MTA. After all, the MTA has to support all functional capabilities of sendmail, so there is a small probability that it might work. The people who have access to the source (Sun Engineering) should test the exploit rapidly and put out an official statement whether MS users need do anything to mitigate this risk. Barring an official statement, every MS site is left in the dark and could potentially be compromised.