Emails from amember script not making it into gmail, what to do?

I have Clickbank integration configured to "accept Direct Payments"

I've made test purchases successfully however the email for new subscribers, containing the login details is not getting through to gmail.

Not even making it into the spam folder. I've made sure the signup email for the test purchase isnt already a member.

Test email from the amember CP also not being delivered to gmail

I did a test purchase with a hotmail account and the signup email (with login details) was delivered, so was the test email.

Why aren't any emails sent from amember CP making it into gmail?

What can I do about it?

Thanks,
Murray