Interia Poczta is a webmail service of the Polish web portal Interia.pl. Users read and send email through a browser, and the login page advertises ample capacity and large attachments. The service is offered as a personal account rather than as a business email product.
The service is operated by Grupa Interia.pl, a company group based in Poland. Poland is an EU member state and the GDPR applies to the operator, but the hosting location of mail data is not stated. For business email, a European organisation would usually choose a service with a documented data processing agreement. Anyone considering the service for work-related messages should therefore ask in writing where mail is hosted and on what terms data is processed, and check how a mailbox can be exported if they later want to move to another provider.