Add the following function (as an optional check before sending a mail) to KMail:

- KMail checks the attachments whether it's filename suffix matches one of those from the according MIME type
- If there is no match found, KMail suggests to add a suffix to the name of the attached file (presents the defined suffixes for selection)

Why is this needed?
- I've seen a lot of people running into the problem 'Hey guy, you've sent me a corrupted file, I can't open it here on Win*!' when Linux users are communicating with Windoze users and exchange files with them.