Connection could not be established with host

Hello, I run a shop, and want to use an email with a provider, I do not want to send an email for sever, but directly over the provider runbox.com When I enter my SMTP data in the shop, I always get this error Error: Please check your settings Connection could not be established with host mail.runbox.com [# 0] I have also tried other providers, how can I adjust ..? The shop is a prestashop. is it because of v = spf1 entry .. ??