Are there any alternatives to Verisign for encrypted email for MacOSX? We tried Verisign already. It didn't work with Entourage and/or the Exchange server. Their customer service was so abysmal and nonresponsive that we demanded our money back.

It's the organization's executives who use Entourage. From everything I've read, this is a known-bug with Entourage, but I don't think abandoning it is going to be a popular option.

Does anyone else provide Mac-compatible certificates?