There are several ways to send your emails:
Using email clients (Gmail, Outlook, etc.)
Using Webmail interface
Using contact forms and different plugins
Using custom PHP scripts
Different ways to send email are using different technologies and ways to deliver your message. Also, different resources are provided to them.
If you are sending emails with webmail or email clients, you are using Hostinger emails. If you are using SMTP with your custom scripts, plugins, or contact forms, and connect to Hostinger email’s servers, you are using Hostinger emails as well.
If you are sending emails with a simple Sendmail or phpmail() function without connecting to external email providers, you are using Web hosting emails.