I am currently upgrading reports from SSRS 2008 R2 to SSRS 2014. I originally opened the reports from 2008 R2 and then saved them to 2014. This worked fine for all the reports...except one.
All the reports I am upgrading are being emailed as MHTML through subscriptions. Everything works in SSRS 2014 except for one report that is being emailed as text (it really looks like a one column HTML table with no formatting or anything). This problematic report has multiple columns of which one is a text field showing comments from a user. Sometimes this comments field can get really big.
As a test, I decided to eliminate the comments field from the report and email the report to myself as MHTML. This worked successfully. There is something about the comments field that is preventing the email from being sent as MHTML. I thought it might be a size issue so I only showed the first 500 characters of the comment and the email was sent as text again instead of MHTML.