How to address a formal letter if unsure of gender?

[volcs0]

Ok. Thanks everyone. I had to send it before the AM - it went out at 4AM - so before I saw the morning responses.

Through google and facebook, I was able to come to about 90% certainty that it is a woman, but I didn't want to take a chance.

Calling the switchboard would have been a good idea. I'll have to remember that.
Also, the standard Memo format is good.

I used:

Greetings.

Thanks for the advice.