What Are Ports 139 And 445? SMB has always been a network file sharing protocol. As such, SMB requires network ports on a computer or server to enable communication to other systems. SMB uses either IP port 139 or 445. Port 139 - SMB originally ran on top of NetBIOS using port 139. NetBIOS is an older transport layer that allows Windows computers to talk to each other on the same network. Port 445 - Later versions of SMB (after Windows 2000) began to use port 445 on top of a TCP stack. Using TCP allows SMB to work over the internet. https://www.varonis.com/blog/smb-port SMB Ports 139 and 445 are open Email Ports 25 and 110 are closed Therefore "D. Email Ports are closed on the Server."