Enforcing line length limit for locally delivered mail

[Markus Schöpflin]

Hello,

were running a few mailing lists with news gateway using postfix for the 
MTA. So the setup is like this: postfix -> mailman -> innd

Now the problem is that sometimes mails exceeding the 1000 characters line 
limit are handed over to postfix, which happily forwards them to mailman 
which in turn sends them to innd, and innd rejects them because the lines 
are longer than 998 characters.

So is it possible to get postfix to do the SMPT line length limit handling 
(split long lines and insert CR LF <blank>) for this kind of setup?

TIA,
Markus