Hello, we’ve recently noticed that our email are being rejected by destinations protected by Cisco IronPort. The rejection message is typically as follows:
host mx1.hc268-98.eu.iphmx.com[207.54.67.223] said: 550 #5.7.1 Your access to submit messages to this e-mail system has been rejected. (in reply to DATA command)
We've checked our IPs and domain reputation are good. What can we do?
