starttls-extra-arguments

starttls-extra-arguments is a variable defined in `starttls.el'.
Its value is

nil

Documentation:
Extra arguments to `starttls-gnutls-program'.
These apply when GnuTLS is used, i.e. when `starttls-use-gnutls' is non-nil.

For example, non-TLS compliant servers may require
'("--protocols" "ssl3"). Invoke "gnutls-cli --help" to
find out which parameters are available.

You can customize this variable.

This variable was introduced, or its default value was changed, in version 22.1 of Emacs.