Could not open socket

Trying to get this to work – with no success. Sending a test email just results in:

‘Could not open socket’

My settings are correct:

SMTP: mail.yourdomainname.co.uk
User Name: email address
Password: The password for the mailbox

Port 587

I’ve tried different security settings – password, plain, etc. None work.

Any ideas anyone?

Thanks,

Mike