Deltacopy and sending email..Error Unable to send message

I have deltacopy installed on two windwos computer...on one of them i do the test for the email notification and test is succesfull and i get my emails after it does rsync..i use smtp.gmail.com, on the other i get an error messgae when i test: "unable to send message. 530 5.7.0 Must issue a STARTTLS command first. bv23sm1005379qcb.19". Can anybody help me on why i am getting this on one computer while the otehr works fien?