"Send Email" action won't send to shared mailbox

My IT group has a shared mailbox setup in Outlook, and I'm trying to use that as the default "To" address for the default send email action. However, the email never seems to get sent to the address. If I use my email, or my boss's email in the box it works fine. But when I send to the shared mailbox it doesn't seem to send anything. Do I need to do something special to make it send to a shared mailbox?