Test email fails to send

I’ve just taken over as admin on an existing site and installed the BackWPup plugin.

The only change I’ve made to the default settings so far is to select [Backup sent via email] and set the email address accordingly.

When I click on [Send test email] I get a spinning icon that doesn’t go away and no test email is received.

Any suggestions?

https://wordpress.org/plugins/backwpup/