Ios mail messages have no content on only one of my two email accounts

Question

I have two email accounts set up on my business servers.  I use Yosemite on my 2014 Macbook Pro and IOS 8.1.3 on my fairly recent Ipad and Iphone 5.  I use the Apple Mail app to send and receive mail on my computer and IOS devices.
My IT person recently made some changes to one of the accounts.  Previously email sent to one of my accounts (call it Account A) was forwarded through another account (call it Account B).  He changed it so that email sent to account A goes directly to my inbox. 
The problem is this:  while I can send and receive email from both accounts on my computer, on my IOS devices, only account B is working properly.   Email sent to Account A results in the  subject line appearing but after a few seconds each email message sent to account A indicates that "This message has no content."  I realize that this often happens with IOS using apple mail, but rather than this being periodic, it now happens with all email to account A.  Logging out of Mail and restarting the device does not affect this.
So email to Account B works perfectly on my Macbook Pro and ios devices.  New email to account A works perfectly on my Macbook Pro, but not on my IOS devices.  Old email to Account A from before the change also appears normally in my inbox. 
The account settings are correct.  I even took it to a Genius Bar to review and they agreed the settings were right.   They were stumped and said it has to be something the IT person did in setting up the account.  But he says both accounts are set up identically.  Apple support on the phone is stumped as well. 
Any suggestions would be welcome. 

Answer 1

Thanks for replying so quickly, but I saw that post earlier. I followed those instructions that were possible, but the instructions for disabling scanning of TB files and folders use menus that I don't have, and the menus I do have don't seem to let me exclude entire folders. In any case, simply disabling the extension eliminated the freeze problem short-term, and re-installing McAfee from scratch allowed me to enable the extension without freezing.
In any case, I'm not asking about the freezing problem -- that was already solved. I'm asking about how to get the extension to recognize two different email accounts.