I've checked the OpenSSL version on our Protectors. This is currently 0.9.8j which is NOT affected by the Heartbleed bug as far as I have been reading on the internet.
However, I cannot find an (clear) official statement from IBM on this.
I find these :
but they are IMHO not very clear on the Protector systems. The closest reference is on the bottom of the second URL with "Proventia Network Mail Security System".
Maybe a good idea to complete the list?