block upload picture via mail

[zomer-g]

When uploading a new item via email, it attaches the photos in the email (usually technical matters of signing by email).

Sometimes we want to upload a photo via email, but this is the exception. If you can distinguish between photos that are part of email signatures and an attachment, that good. If not, then it is better to completely block image files for uploading by email (and leave the option of course to attach as a file to an existing item the old way).