Here's a tip: "Don't do it". Does your whole database need to know every time you hire a new executive or win an award? Perhaps but you should really consider what you send and how you send it because email recipients these days no longer have the same patience as they once had. They expect to receive relevant and timely information that they have subscribed to. Before you know it, you'll have a bunch of unsubscribes and when you really do have relevant information, you'll miss out some key prospects/customers as they've already opt-ed out.
My suggestion would be to include press release snippets as part of a monthly or quarterly newsletter that has additional value added content. In this way, you cut down on the frequency of your emails and you provide content in a more regular format that your email subscribers expect to receive.
PS: Here is a great article from Demand Gen Report that speaks to some of the points above in terms of using and not abusing your email list: Building & Leveraging A New Email List From The Ground Up