Customer not receiving Order Confirmation email

[babymaxi]

Hi,

When an order is placed, the shop email inbox does receive the "New order" email. But the customer doesn't receive the Order Confirmation email.

I've tried these instructions but still no solution.
http://www.presto-changeo.com/content/9-fix-email-problems

I've tried ordering from Hotmail and Gmail.
I've removed the [ shop name ] brackets from the subject line.

Interestingly though, the customer does receive the "Out of stock" email. That could give a clue.

Looking forward to some help.

Thank you.
Basile