List of authentication sources.
The default will get login and password information from
"~/.authinfo.gpg", which you should set up with the EPA/EPG
packages to be encrypted. If that file doesn't exist, it will
try the unencrypted version "~/.authinfo" and the famous
"~/.netrc" file.
See the auth.info manual for details.
Each entry is the authentication type with optional properties.
It's best to customize this with `M-x customize-variable' because the choices
can get pretty complex.