Permitted attachment types

[3298]

Okay, that's a hurdle I did not expect. I have next to no knowledge about that stuff, but after reading up on it, I'd go with the generic "application/octet-stream". (At least my mail client chose that when I sent a mail with .hp and .ex3 attachments to myself.) If that is not satisfactory, a type will have to be made up and registered - while searching through the list of registered types, I couldn't find a matching type other than that generic one.