I need to separate natural, coherent text/sentences in emails from lists, signatures, greetings and so on  before further processing.
example:

Hi tom,
last monday we did bla bla, lore Lorem ipsum dolor sit amet, consectetur adipisici elit, sed eiusmod tempor incidunt ut labore et
  dolore magna aliqua.

list item 2
list item 3
list item 3

Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquid x ea commodi consequat. Quis aute iure reprehenderit
  in voluptate velit
regards, K.
---line-of-funny-characters-#######
example inc. 
33 evil street, london
mobile: 00 234534/234345

Ideally the algorithm would match only the bold parts. 
Is there any recommended approach - or are there even existing algorithms for that problem? Should I try approximate regular expressions or more statistical stuff based on number of punctation marks, length and so on?
In the example you post, line length suffices. 
There is no perfect algorithm; even human beings will classify lines differently. 
I suggest just use line length until you find a counter example, at which point revise your algorithm. Repeat until problem solved to your satisfaction.
Algorithm to match natural text in mail