Microsoft Knowledge Base Article 310298 contains the following summary:
This article describes how to use Portqry.exe to troubleshoot Microsoft Exchange Server connectivity issues. You can use the
Portqry.exe command-line utility to troubleshoot TCP/IP connectivity issues. Portqry.exe runs on Windows 2000.
Portqry.exe reports the port status of target TCP and UDP ports on a remote computer.
You can use Portqry.exe to troubleshoot Microsoft Exchange Server issues where basic TCP/IP connectivity must be verified. This may be useful in environments that have firewalls. You can use Portqry.exe to verify connectivity to TCP/IP ports that are used by Exchange Servers for SMTP, POP3, IMAP, LDAP, RPC, NetBIOS, and DNS.
Note Version 2 of Portqry.exe is now available. The Microsoft Download Center link at the end of this article has been updated to reflect the new version. Version 1.0 of Portqry.exe has been removed from the Microsoft Download Center.