Corporate PGP for network operators

Ok, extremely dumb question. But I'm sure lots of other people have already solved this one. Network operators have been using various PGPs to exchange confidential information for many years. I have my own personal PGP key for my own use and a nice Unix box of my own. There are licensed versions, freeware versions, guerilla versions, and so forth. NAI is no longer selling a commercial version of PGP Desktop for Microsoft Windows/NT. Phil Zimmerman points people to the OpenPGP alliance http://openpgp.org/members/ What do commercial network operators, who are required to use Microsoft, use for business PGP mail besides NAI? I.E. if we need to exchange PGP mail, what package is least likely to crash Outlook and Windows.