To ensure reliable deliver of email from your website, there are some best practices to observe.
In Backlight's Settings:
Your host should be aware of the above email address; create an email account in your host's control panel matching the sender's access. You do not need to use the host to manage the email 1)
, but this makes the host aware of it being a valid address, so that it will trust Backlight's attempts to send mail using the address.