Apart from the general (and rather misleading) statement that e is pronounced
closed when followed in the next syllable by a closed front vowel or diphthong,
a palatalized consonant or j, and is otherwise pronounced open, a rather
complex formulation is required to predict the occurrence of open and closed e.
For basic guidance, however, see A Synchronic Approach. These rules do not
extend to bez, ne, etc., used as prefixes, where the quality of e does not normally vary
from the closed pronunciation heard when these words are independently
used. Ne, however, when prefixed to a word beginning with open e or open Á ā
will itself usually be pronounced with open e; thus:
neesmu is often pronounced (neesmu)
neÁrts is often pronounced (neÁrts).

T.G.Fenell. H. Gelsen