I have received reports from several people that when they send an email to our domain (beekersoft.com) they get an email back stating that it was rejected by the server. Their domain is in our trusted sender list for the postmaster account and other accounts use the default spam settings so it should be getting through. We used to get their emails and suddenly this started happening. Why would this be happening and how do we fix it?? Does it have to do with SPF and grey lists??