How can I abort a SMTP send operation with Synapse for Delphi?

Question

At the moment I am testing Ararat Synapse to send e-mails in Delphi.

A local function creates a TSMTPSend and sends the e-mail.
How can I abort this operation? I have set a callback function assigned to SMTP.Sock.OnStatus to perform some status output.
When I want to abort the send progress, I thought I could use the TTCPBlockSocket of the TSMTPSend within the callback function because in this function I have no access to the TSMTPSend directly.

What I wanted to do looks basically like

MyCallBack(Sender: TObject; Reason: THookSocketReason; const Value: string);
begin
  if FCancelWasClicked then
  begin
    if Sender is TTCPBlockSocket then
      TTCPBlockSocket(Sender).StopFlag := True;
      // or TTCPBlockSocket(Sender).AbortSocket or CloseSocket
  end;
end;

But StopFlag shows no effect and AbortSocket/ CloseSocket lead to a StackOverFlow because the socket will then be pumping HR_CloseSocket messages endlessly.

Am I doing it wrong? Are there other options?

Answer 1

Synapse provides a heartbeat function, which allows implementation of Cancel behaviour.

http://www.ararat.cz/synapse/doku.php/public:howto:heartbeat

Handle the OnHeartbeat event, set the HeartbeatRate property to the interval between heartbeats, and set the StopFlag to cancel the operation.