CiviCRM Community Forums (archive)

If I use the Send an email feature to send to a particular contact or selected group of contacts, people may assume incorrectly that providing either HTML or plain-text will come through fine for their recipients given their experience of choosing either one or the other in most email clients. However, providing only HTML content to be sent to recipients marked to receive only plain text, or providing only plain text content for recipients marked to receive only HTML message leads to empty messages being sent out.

Would be best to prevent this from being sent or at least warn sender of problem. I imagine this happens inadvertently sometimes, so a warning would make a big difference.