This used to work for me as the ISP had an open smtp server - but i have swapped ISP, and no longer have that luxury 
To that end - i am trying to utilise my web hosts smtp server, but it requires a username, and password, and tls
So I’ve got postfix installed, and i have followed a number of online tutorials - but i just can’t get it to work - can anyone point me in the right direction at all ?