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So you do not think that the behavious that I have outlined 
is a bug? To me it clearly shows that roundup will have to 
record the charset to be able to display those attachments 
in a browser or per email correctly. 
 
It is not a hard bug not having a charset in an email, but 
it leads to a bug for the users, because the umlauts will 
be broken. I have this on a live system. 
 
I also have the problem with web browsers, btw, 
because roundup does not know the charset, it cannot give 
it to the browser, who will then display the texts wrong. 
 
How do you envision to fix the bad behaviour without saving 
the charset? I created a case that will occur often in 
non-us environments and will lead to broken behaviour (for 
the users).