line brake for attachments

[Dieter Faulbaum]

if I attach a file, I always have a newline in the message buffer 
like this:
(the backslashes are only there to not interpret the part (before 
sending))

<\#part ...>
<\#/part>"

for me it would be (much) nicer if this attachment needs only one 
line like this:

<\#part ...><\#/part>"

Is it possible to have a (customizable) variable for this 
behaviour?