Unable to connect IdPop3 to IdPop3Server via SSL - delphi

Question

I have a TIdPop3Server in one application that has a IdServerIOHandlerSSLOpenSSL1 attached to it and retrieves emails and sends them to a TIdPop3 client in another application (having TIdSSLIOHandlerSocketOpenSSL attached to it). Everything's fine when the connections are made insecure using port 110. But when I try to use SSL connection through port 995 I get error Connection Closed Gracefully after connect attemp from the client fails. This is my Pop3SeverOnConnect event :
procedure TMainForm.Pop3ServerConnect(AContext: TIdContext);
begin
if (AContext.Connection.IOHandler is TIdSSLIOHandlerSocketBase) then
TIdSSLIOHandlerSocketBase(AContext.Connection.IOHandler).PassThrough :=
(AContext.Binding.Port <> 995);
showmessage('SSL connection made!');
end;
And this is the client-side :
procedure TMainForm.btnCheckMailBoxClick(Sender: TObject);
begin
IdSSLIOHandlerSocketOpenSSL1.PassThrough := False;
POP3Client.IOHandler := IdSSLIOHandlerSocketOpenSSL1;
with POP3Client do begin
AuthType := patUserPass;
Host := myHost;
UserName := myUserName;
Password := myPass;
Port := myPort;
end;
try
POP3Client.Connect;
Except on e : Exception do
showmessage('error=' + e.Message);
end;
// code for retrieving message data
end;
And I always get an exception from Pop3Client.Connect like I've already mentioned above (The message SSL connection made! in the server application never shows up). If I use however another mail client like for example Mozilla Thunderbird I achieve a successful SSL connection for port 995. So the problem should be somewhere in the client's procedure but who knows - that's why I'm asking you guys for help.

Answer 1

In your client code, you need to set the TIdPOP3.UseTLS property instead of the TIdSSLIOHandlerSocketOpenSSL.PassThrough property directly, eg:
procedure TMainForm.btnCheckMailBoxClick(Sender: TObject);
begin
with POP3Client do
begin
IOHandler := IdSSLIOHandlerSocketOpenSSL1;
AuthType := patUserPass;
UseTLS := utUseImplicitTLS; // <-- here
Host := myHost;
UserName := myUserName;
Password := myPass;
Port := myPort;
end;
try
POP3Client.Connect;
try
// code for retrieving message data
finally
POP3Client.Disconnect;
end;
except
on e : Exception do
ShowMessage('error=' + e.Message);
end;
end;
In your server code, you need to get rid of the ShowMessage(). TIdPOP3Server is multi-threaded, the OnConnect event is fired in the context of a worker thread, and ShowMessage() is not thread-safe. If you must display a popup message, use Windows.MessageBox() instead.