>>> "Andreas" == Andreas Schwab <schwab@linux-m68k.org> writes:

> On Okt 01 2018, Uwe Brauer <oub@mat.ucm.es> wrote:
>> Here comes the error message:
>> 
>> Debugger entered--Lisp error: (wrong-type-argument characterp 134217766)
>> auto-capitalize(43 44 0)
>> #f(compiled-function (header value) #<bytecode 0xfad401>)(To "SERGIO MARRERO PEREZ <smarrero@ucm.es>")
>> mail-header-format(((From) (Newsgroups) (To) (Cc) (Subject)

> What is this auto-capitalize function?  Did you change the value of the
> mail-header-format-function variable?

Auto-capitalize is a quite old code written by Kevin Rodgers, and auto
capitalize text. It is in my message-mode-hook 
(org-contacts-setup-completion-at-point my-refill-key
th/gnus-article-enable-prettify footnote-mode outline-minor-mode
turn-on-auto-capitalize-mode turn-off-electric-indent-mode orgalist-mode
turn-on-quail-latin-1 turn-on-mysmiley my-msg-keys-mule
turn-on-auto-fill turn-on-flyspell)

But that should not interfere with the reply function?!

Uwe