Confirmation email not being sent to new subscribers

I have a phpList installation (v3.3.1) installed by the Softaculous software available from a SiteGround hosting account. I have been able to send a test campaign message to my email address. However when I subscribe (under another email account of mine) I do not receive the email to allow confirmation of the subscription. I tried again with a third email address and again there was no confirmation email. I presume the same mechanism is used to send out the test campaign email as is used for the confirmation. How do I find what has gone wrong please?