If your company can afford to implement the call back method by having someone available to answer phones then this method would be the fastest and most reasonably secure. You may also want to consider using something else to verify the individuals identity with the company and to make reference other than the call back number i.e. employee number, etc...

Note: If your company is large you may want to implement the voice mail method with the same specifications as above. Although this method will be slower than the above listed method because the user will not get the pw immediately. Although, it should still be satisfactory enough to get the job done.

-neta1o-