Office generic email allstaff@company.com that goes to all emails?

I have an office of about 70 employees each with an individual email. We are looking to set up a unique email address that will be the used to email everyone in one email address. My example: We are having a company picnic on Saturday. We would email allstaff@company.com or some email we make up. This would be an email that all would know to be able to reach every employee without haveing to remember the others email addresses. I would appreciate any assistance on how to do this or does the email server company IT person set this up. Not Yahoo but a company email system. Thanks.