is a list of recipient certificates. B<in> is the content to be encrypted.
B<cipher> is the symmetric cipher to use. B<flags> is an optional set of flags.
-=head1 NOTES
-
Only certificates carrying RSA, Diffie-Hellman or EC keys are supported by this
function.
B<CMS_DETACHED> is set in which case it is omitted. This is rarely used in
practice and is not supported by SMIME_write_CMS().
-=head1 NOTES
-
If the flag B<CMS_STREAM> is set the returned B<CMS_ContentInfo> structure is
B<not> complete and outputting its contents via a function that does not
properly finalize the B<CMS_ContentInfo> structure will give unpredictable