Using notmuch in mutt searches on the from field often return too few
hits. I see more mails by using the limit command of mutt.
In order to be sure that mutt does not get in the way of my notmuch
search I tried directly from the command line (notmuch search), same
problem.

notmuch config list returns:

    new.tags=unread;inbox;
    new.ignore=
    search.exclude_tags=
    maildir.synchronize_flags=true
    crypto.gpg_path=gpg
    built_with.compact=true
    built_with.field_processor=false
    built_with.retry_lock=false
Helmholtz-Zentrum Geesthacht 
Zentrum für Material- und Küstenforschung GmbH 
Max-Planck-Straße 1 I 21502 Geesthacht I Deutschland/Germany 

Geschäftsführer/Board of Management: Prof. Dr. Wolfgang Kaysser, Dipl.-Ing. Michael Ganß 
Vorsitzender des Aufsichtsrates/Chairman of the Supervisory Board: Ministerialdirigent Dr. Herbert Zeisel 
Amtsgericht Lübeck HRB 285 GE (Register Court) 
Internet: http://www.hzg.de