I need a function that breaks all lines marked at 40 chars

[gerlach]

Hi,

I'm writing mails with emacs and I sometimes want to
break all text lines that I marked to say 40 chars.
But empty line (only returns) should not be filled to
40 chars. Entire words should not be cutted within the
word.

Can you help me writing such a function? I'm beginner ...

I want:
 1. mark the the text I want to break at 40 chars
 2. call a function (M-x .... ???? )
    and the text ist breaked

Perhaps emacs has such a function already build-in. Where?

The function may be placed in .emacs profile with hard
coded number of chars , e.g.  40

tia
Eckard