I noticed today that an email for one of our clients was working great across the board, apart from on Outlook.com in browser. What is happening is the header part of my message isn't being rendered, so the rest of the email is being pushed up. The part in particular that is getting ignored is wrapped in <mso> code, yet strangely other sections of the email that contains <mso> do work...

After a bit digging, I found a discussion from a few years back that had a similar issue, which was put down to <mso>, yet their solutions didn't work in this case, and I kind of ruled out that the issues were related.

Anyway... I sent out a few more tests to colleagues, and it worked perfectly for one recipient. We noticed that when the email doesn't render correctly, it is for accounts that are migrated onto the Outlook.live.com domain, whereas when the email does render correctly, it is for users on the older dub129.mail.live.com domain.

Has anyone noticed anything similar? I'm looking into a solution now and will update if I find a fix, I'm guessing some of you will / will already have come across this issue!