Yes, it's all about diferent Content-Type
I tried to send it by Outlock express and it works!
Outlock:
Content-Type: application/octet-stream;
name="eicar.com"
Content-Transfer-Encoding: 7bit
Content-Disposition: attachment;
filename="eicar.com"
Mozilla:
Content-Type: text/plain;
name="eicar.com"
Content-Transfer-Encoding: 7bit
Content-Disposition: inline;
filename="eicar.com"
Thanx for help.
RaBL