Hostinger email account configuration is:
Incoming Server name (pop3): pop.hostinger.com
Port number: 995
Incoming Server name (IMAP): imap.hostinger.com
Port number: 993
Outgoing server name (SMTP): smtp.hostinger.com
Port number: 465 or 587
Encryption: SSL/TLS or StartTLS
Note: Based on where you purchased your hosting, the email configuration will differ, for example, imap.hostinger.in, smtp.hostinger.in, and pop.hostinger.in for Hostinger India.
You can always see default email configuration for your account by navigating to Hosting → Manage → Email Accounts section:
Correct email configuration will be indicated in the E-mail details section:
Alternatively, you can find the same configuration by navigating to Hosting → Manage → Details section.