Principals/admin who don't reply to emails...

Anyone experienced this? I have a principal (male, 50s) who doesn't answer his email at times. I sent him an important email a week ago, and with no response, it's kind of stressful. Anyone have any tips? Commiseration? Stories? Cheers

Edit: Thanks all for the comments. I'm actually pleased (and frustrated) that many others have experienced the unresponsive administrator. But now I have some strategies to work with, and I'm putting my principal on an unofficial specialized learning plan he knows nothing about.