Some but not all incoming emails are being bounced
All of a sudden some incoming emails from outside clients (approx 10 different companies) are being bounced back to the sender with the message: you do nothave permission to send to this recipient. The helo/ehlo domain is invalid.
1) I have checked that the FQDN on the server matches that of our MX record etc & it all checks out ok.
2) I have spoken with our ISP & they have not put through any changes that would affect this.