compose-mail-user-agent-warningscompose-mail-user-agent-warnings is a variable defined in `
simple.el'. Its value is
tDocumentation: If non-nil, `compose-mail' warns about changes in `mail-user-agent'. If the value of `mail-user-agent' is the default, and the user appears to have customizations applying to the old default, `compose-mail' issues a warning. You can customize this variable. This variable was introduced, or its default value was changed, in version 23.2 of Emacs.