How to set stuff like From, Organization, Reply-To, signature...?
There are other ways, but you should use posting styles for this. (See below why.) This example should make the syntax clear:
(setq gnus-posting-styles '((".*" (name "Frank Schmitt") (address "me@there.invalid") (organization "Hamme net, kren mer och nimmi") (signature-file "~/.signature") ("X-SampleHeader" "foobar") (eval (setq some-variable "Foo bar")))))
The ".*" means that this settings are the default ones
(see below), valid values for the first element of the
following lists are signature, signature-file,
organization, address, name or body. The attribute name
can also be a string. In that case, this will be used as
a header name, and the value will be inserted in the
headers of the article; if the value is nil
, the header
name will be removed. You can also say (eval (foo bar)),
then the function foo will be evaluated with argument bar
and the result will be thrown away.