Deleted messages from any Hostinger email folder are automatically moved to the Trash Folder, where they are kept for 30 days. To recover a deleted message, open your email account via Webmail, click on the folder icon, and select Trash:
Next, select the message and click on More → Move to... → Inbox:
Once a message is deleted either over 30 days ago or manually from the trash folder, it cannot be restored as it is permanently removed.
If you are using an email client and you are not leaving copies on the server, you can try to recover deleted messages by following the corresponding guide: