🚀 go-pugleaf

>> The search for vm-mime-encode-headers-words-regexp in
>> vm-mime-encode-headers may fail, depending on the user's case-table.
>> Setting case-fold-search to nil will prevent this.

> How could it fail if both lower and upper case are within the
> character searched class? 

It can fail since equivalence for search is controlled by the
CANONICALIZE and EQUIVALENCES slots of the case table, and there is
more to it than upper and lower case (see section "4.9 The Case Table"
in the Elisp reference manual).

To reproduce the problem, evalute the following lisp expression and
then send an e-mail with a subject containing Umlaut characters, e. g.
"Subject: ���". No MIME encoding of the subject will take place.

   ;; Ignore accent and umlaut marks when searching.
   (let ((eqv-list '("aA������������"
                     "cC��"
                     "eE��������"
                     "iI��������"
                     "nN��"
                     "oO������������"
                     "uU��������"
                     "yY���"))
         (table (standard-case-table))
         canon)
     (setq canon (copy-sequence table))
     (mapc (lambda (s)
             (mapc (lambda (c) (aset canon c (aref s 0))) s))
           eqv-list)
     (set-char-table-extra-slot table 1 canon)
     (set-char-table-extra-slot table 2 nil)
     (set-standard-case-table table))

> Anyway, it should not harm to set case-fold-search to nil ;-)

Exactly. ;-)

Ulrich