camel mail: content-transfer-encoding configurable

Hello,

the camel mail componente determines the content-transfer-encoding itself
based on the content of the message.
We now have a customer we are only allowed to send messages where the
content-transfer-encoding is base64. As most of the messages haven't any
special characters camel determines 7bit or quoted-printable as
content-transfer-encoding and we are not able to manipulate that.

I wanted to discuss if content-transfer-encoding would be a viable uri
option(like contentType) for the future.
If so, I would create a ticket and try my best to provide a patch for this.

kind regards,
Christoph