版本不对的原因。
具体在10.5.9下修改此参数即可解决问题。
LoadFunction() has an ACritical parameter. It is set to True by default, but can be set to False for individual functions (and currently is False for TLS 1.1+ and DTLS functions). You can patch IdSSLOpenSSLHeaders.pas to set ACritical to False for the missing SSLv2 functions. As long as you never use sslvSSLv2 in TIdSSLIOHandlerSocketOpenSSL, you should be fine. I will add this to the TODO list for a future Indy release.