Wrong name for site_name in the link preview. Correct site_name should be Europost or europost.gr
"The site_name property must include the correct name of the website. If the webmaster includes unnecessary data (e.g. ‘Site {sitename}’) or mixes the site name with the article title, your template must take care of this."
In this case the webmaster includes "Ειδήσεις και Νέα με Άμεση και Έγκυρη Ενημέρωση" which is considered unnecessary data.
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"The site_name property must include the correct name of the website. If the webmaster includes unnecessary data (e.g. ‘Site {sitename}’) or mixes the site name with the article title, your template must take care of this."
In this case the webmaster includes "Ειδήσεις και Νέα με Άμεση και Έγκυρη Ενημέρωση" which is considered unnecessary data.
https://instantview.telegram.org/checklist#3-2-link-preview