uses Registry;
procedure OpenMailClient;
const
cMailClient = '\SOFTWARE\Clients\Mail\';
var
reg: TRegistry;
RegClientDefault: string;
begin
reg := TRegistry.Create;
try
with reg do
begin
CloseKey;
RootKey := HKEY_LOCAL_MACHINE;
if OpenKeyReadOnly(cMailClient) then RegClientDefault := reg.ReadString('');
if OpenKeyReadOnly(cMailClient + RegClientDefault + '\shell\open\command') then
WinExec(PChar(ReadString('')), SW_SHOWNORMAL);
end;
finally
reg.Free;
end;
end;
procedure TForm1.Button1Click(Sender: TObject);
begin
OpenMailClient;
end;