well i'm sorry to say this probably won't help you but I got my exchange working by resetting the permissions in Active Directory. If you are able to contact your exchange admin then have him open active directory and perform the following. View > Ensure Advanced Features is enabled > Locate the problem user > Properties > Security > Advanced > Tick the box to "Allow inheritable permissions from this objects parent" > Apply.
I also clicked the reset to default. After applying that and then deleting my account from my phone and adding it back in, I was able to get HTML emails.
Also if anyone does this, please do so at your own risk, this is my server so I am responsible for my screw up. I have no idea at this stage if there are any side effects of doing this, so again do so at your own risk, having said that, all seems fine now.
---------- Post added at 06:47 PM ---------- Previous post was at 06:19 PM ----------
It still didn't work, BUT try this. see if it helps.
Go into your account settings for the email.
Click on your "menu" (Three Horizontal lines icon, bottom right)
Choose Reset Settings.
Immediately after doing this I got an HTML Outlook confirmation email. All emails that came in after that were HTML, but older ones, were still in plain text. It's working form this point one basically.
The only other issue i noticed is that when a message is bigger than whatever you set in the max size setting, and you click on Download Entire Message, it will download that message in plain text. Not a great fix, but i thought it might help... it's a start at least.