C++Builder 11.0下Indy 10.6.2.0无法启用TLS 1.1及以上版本

尝试使用仅支持TLS 1.1及更高版本的SMTP服务器发送邮件，但在C++Builder 11.0环境下使用Indy 10.6.2.0时无法启用正确的TLS版本。已将libcrypto-1_1.dll和libssl-1_1.dll复制到应用程序目录，但问题仍未解决。

抛出EIdOSSLUnderlyingCryptoError异常，错误信息为：

error:1409442E:SSL routines:SSL3_READ_BYTES:tlsv1 alert protocol version

相关代码 #

IdSMTP *IdSMTP1;
TIdText *IdText1;
TIdMessage *IdMessage1;
TIdAntiFreeze *IdAntiFreeze1;
TIdAttachmentFile *IdAttachment1, *IdAttachment2;

try {
    Form1->AX0CPos = 109900;
    UnicodeString UX0SNom = " "+ AX0SNom.SubString(0, AX0SNom.Length()-1);

    if(!GAntiFreeze) {
        IdAntiFreeze1 = new TIdAntiFreeze(NULL);
        IdAntiFreeze1->IdleTimeOut = 250;
    }
    Form1->AX0CPos = 109901;
    IdSMTP1 = new TIdSMTP(NULL);
    TIdSSLIOHandlerSocketOpenSSL *IdSSLIOHandlerSocketOpenSSL1 = new TIdSSLIOHandlerSocketOpenSSL(IdSMTP1);
    //IdSSLIOHandlerSocketOpenSSL1->SSLOptions->Method = sslvTLSv1_1;
    // Either Version or Method !!!
    IdSSLIOHandlerSocketOpenSSL1->SSLOptions->SSLVersions.Clear();
    IdSSLIOHandlerSocketOpenSSL1->SSLOptions->SSLVersions << sslvTLSv1_1 << sslvTLSv1_2;
    IdSSLIOHandlerSocketOpenSSL1->SSLOptions->Mode = sslmClient;  // ?
    IdSSLIOHandlerSocketOpenSSL1->PassThrough = false;

    Form1->AX0CPos = 109902;
    IdSMTP1->IOHandler = IdSSLIOHandlerSocketOpenSSL1;
    //IdSMTP1->Host = _D("ssl0.ovh.net");
    IdSMTP1->Host = _D("smtp.mail.ovh.net");
    IdSMTP1->Port = 465;
    IdSMTP1->UseTLS = utUseImplicitTLS; //utUseRequireTLS; utUseExplicitTLS;
    IdSMTP1->Username = _D("MyUserName");
    IdSMTP1->Password = _D("MyPassWord");
    IdSMTP1->AuthType = satDefault;

    Form1->AX0CPos = 109903;
    IdMessage1 = new TIdMessage(NULL);
    IdMessage1->Priority = mpHigh;
    IdMessage1->Recipients->EMailAddresses = "Recipients@Recipients.com";
    IdMessage1->Subject = _D("User #"+ String(CODOPharmacie) + UX0SNom);  // Form1->NRSOPharmacie
    IdMessage1->Encoding = meMIME;
    IdMessage1->ContentType = _D("multipart/mixed");
    IdMessage1->CharSet = _D("UTF-8");
    IdMessage1->From->Address = _D("MyUserName");
    IdMessage1->From->Name = _D("MyApp");
    IdMessage1->AttachmentEncoding = "MIME";

    Form1->AX0CPos = 109904;
    IdText1 = new TIdText(IdMessage1->MessageParts, NULL);
    IdText1->Body->Text = AX0LMes;
    IdText1->ContentType = _D("text/plain");
    IdText1->CharSet = _D("utf-8");

    Form1->AX0CPos = 109905;
    if(FileExists(UX0CPDMyApp + "\OrtErr.log"))
        IdAttachment1 = new TIdAttachmentFile(IdMessage1->MessageParts, UX0CPDMyApp + "\OrtErr.log");
    Form1->AX0CPos = 109906;
    if(FileExists(UX0CPDMyApp + "\HTPErr.htm"))
        IdAttachment2 = new TIdAttachmentFile(IdMessage1->MessageParts, UX0CPDMyApp + "\HTPErr.htm");

    Form1->AX0CPos = 109907;
    IdSMTP1->Connect();
    IdSMTP1->Send(IdMessage1);
    IdSMTP1->Disconnect();
}
catch(Exception &EX0Vl){
    AX0SNom = "Form1/SendEmail/";
    AX0LMes = EX0Vl.Message;
    ORTErr();
}
catch(...)
{
    AX0SNom = "Form1/SendEmail/";
    AX0LMes = "Exception non planifiée";
    ORTErr();
}

• 确认OpenSSL版本兼容性：Indy 10.6.2.0对OpenSSL 1.1的支持有版本细分要求，需使用1.1.1q及以上的小版本。检查当前dll版本，替换为Indy官方匹配的版本。
• 修正TLS配置逻辑：删除IdSSLIOHandlerSocketOpenSSL1->PassThrough = false;这行代码——当UseTLS = utUseImplicitTLS时，Indy会自动处理SSL握手，手动设置PassThrough会干扰流程。保留SSLVersions的配置即可。
• 检查端口与UseTLS的匹配：端口465对应隐式TLS是正确的，但部分服务器可能要求显式TLS（端口587）。尝试切换到端口587并设置UseTLS = utUseExplicitTLS测试。
• 强制TLS版本范围：添加代码限定最小和最大TLS版本，避免握手时协商到被服务器拒绝的旧协议：

  IdSSLIOHandlerSocketOpenSSL1->SSLOptions->MinVersion = sslvTLSv1_1;
  IdSSLIOHandlerSocketOpenSSL1->SSLOptions->MaxVersion = sslvTLSv1_2;
  

• 升级Indy组件：Indy 10.6.2.0存在已知的TLS配置bug，升级到最新的Indy 10稳定版本（如10.6.2.5及以上）可修复此类问题。
• 验证库位数匹配：如果编译的是64位应用，必须使用64位的libcrypto-1_1.dll和libssl-1_1.dll；32位应用则用32位库，位数不匹配会导致SSL握手异常。

内容的提问来源于stack exchange，提问作者ibouka