For the Hitrost.com service provider, the limitation for sending e-mails to a certain country may be set and therefore, adjusting the settings on their website is required.
Log in to your account on their website.
In the control panel, search for and click on "SMTP access limitations".
If limitations for sending to a certain country/-ies are set, including ''Ireland'' is also required (see the picture below).
With such settings, there should be no issues when sending e-mails from MetaKocka.