Cannot view email text on many emails

It says "This message has not been downloaded from the server." The iPhone tech support guy said to delete the original mailbox and set up a new one ....that didn't solve the problem. In the inbox, I can see who sent the email and what the subject line is but the email says 'This message has no content" then I select that email and it gives me the "message not downloaded" message. I don't understand why it only happens on some rather than others; it happens on about half of the emails I get on both my home and my office email addresses. Can you help? Thank you! Judy