While connected from home to an ISP (Internet Service Provider), a network administrator performs a port scan against a corporate server and encounters four open TCP (Transmission Control Protocol) ports: 25, 110, 143 and 389. Corporate users in the organization must be able to connect from home, send and receive messages on the Internet, read e-mail by beams of the IMAPv.4 (Internet Message Access Protocol version 4) protocol, and search into a directory services database for user email addresses, and digital certificates. All the e-mail relates services, as well as the directory server, run on the scanned server. Which of the above ports can be filtered out to decrease unnecessary exposure without affecting functionality?