Apple Mail Pulling Wrong Exchange Server Details

My company just switched their email from a hosted Exchange Server to Office 365. I deleted my email address and then tried to set it up as a new Exchange account. On my iPad and iPhone, it worked fine. However, on my iMac and MacBook Pro, Apple Mail is populating the old server address. I can't seem to find a workaround. Is there a way to completely delete any old information related to the old mail server so Mail is forced to discover the correct server address for the new Office 365 account?