Blat 3.2.1 64 bit 'hangs'

Hello there,
 

 I am trying to send automated mails via blat, unfortunately the system stucks.
 The details:
 Blat 321 64 bit, actual version, downloaded 2014-07-14, running on Windows Server 2012 R2. 
 The batch file:
 

 set BlatProg=C:\Windows\...\Blat.exe
 

 set to_Mail=***
 set my_Mail=***

 set Mail_Server=***
 set Mail_Server_Password=***
 set Mail_Server_Login=***
 

 call %BlatProg% -to %to_eMail% -f %my_eMail% -server %Mail_Server% -u %Mail_Server_Login% -pw %Mail_Server_Password% - debug -subject enemenemuh

 

 The effect: The batch file is executed and hangs after echoing the command line. Debug information is not available. ^C is  accepted and prompts 'Cancel batch file Y/N?' 
 

 Has anybody got an idea of how to solve the problem?
 

 Thanks in advance!