Hi I finally got a chance to look at the problem with the person who trying to email me. I've raised the rejection header with the outlook.com team. Looks like some sort of socket closed error in the guts of outlook.com after 26 retry attempts.
I'm hoping it's just some sort of bad configuration or SPF related issue.
The only other thing is virginmedia is actively blocking stuff based upon misconfigured SPF config.
I'll upload the headers later when I have them, redacting certain bits.
I don't have the rejection header at hand, but once I have access to it I'll be able to share it. Microsoft support are also on the case looking into the problem. As I say last successfully received message from that contact was about 3 weeks ago from their hotmail.com email (via outlook.com), to my blueyonder.co.uk account.
Just for the record. While I won't have a blueyonder address much longer, I am still able to test for the next day or so. I did do a test from an outlook.com address to my blueyonder address. Note that outlook.com and hotmail.com addresses are sent via the same server set (much like the different VM domains all use one set of servers). So from what I can tell it's not a general IP block Blocks don't normally run based on domains, and hotmail.com currently runs with a DMARC policy of p=none, so an SPF or DMARC fail SHOULDN'T cause an outright rejection.
We really need to see the rejection message (can you get it sent via a third party email?) These carry important information as to why VM chose to reject the mail.
I'm a Very Insightful Person, I'm here to share knowledge, I don't work for Virgin Media. Learn more
Have I helped? Click Mark as Helpful Answer or use Kudos to say thanks