Set PrefEmailID on External Users ?

[maguirre]

Is there a way to set Preferred e-mail address (PrefEmailID) to external users? I have the GW Gateway for MS Exchange and I want to change the PrefEmailID to all exchange contacts.

I can do it using ConsoleOne, but there are 60,000 external users, so change it manually is not an option.

TIA.

Mauricio