Оформил: DeeCo
Автор: http://www.swissdelphicenter.ch

{ 
  Kommando ermitteln, mit welchem ein bestimmter, 
  installierter Mail-Client gestartet werden kann. 

  Get command to start a specific, installed Mail-Client. 
}

 uses
   Registry;

 function GetMailClientOpenCommand(AMailClient: string): string;
 const
   RegClientsRoot = '\SOFTWARE\Clients';
   RegClientsMail = '\Mail';
   RegClientsOpenCmd = '\shell\open\command';
 var
   reg: TRegistry;
 begin
   Result := '';
   reg := TRegistry.Create;
   try
     with reg do
     begin
       CloseKey;
       RootKey := HKEY_LOCAL_MACHINE;
       if OpenKeyReadOnly(RegClientsroot + RegClientsMail +
         '\' + AMailClient +
         RegClientsOpenCmd) then
         Result := reg.ReadString('');
     end;
   finally
     if Assigned(reg) then reg.Free;
   end;
 end;