I have been having issues with not receiving replies to an email I sent out to my road marching team re: Cosford. However, I can find no reason nor rhyme as to which accounts or which providers are bouncing.
Two weeks ago the spam filter level was increased and it was blocking lots of domains including Hotmail email addresses and my own Sqn email addresses. I put in requests via Bader Helpdesk to resolve both of these. Logs4a has been responding to these types of service requests fairly quickly so put one in if you’re still finding these problems are occuring.