Network clients use email applications to connect to an online email provider, because your company does not currently host this service. A virus outbreak in the network has caused the email clients to begin sending spam emails to everyone on the client’s distribution lists. What port on the router can be disabled until the problem is fixed, to prevent further spam?

Simple Mail Transfer Protocol (SMTP) is typically the standard protocol that is used by email clients to send emails. In the event that a virus caused the email clients to send emails from the users’ computers, you could block port 25 traffic. This action will stop the emails from being sent.

21:
File Transfer Protocol (FTP) is a protocol used to transfer files from an
FTP-based server to your computer. This protocol uses port 21. Blocking this port number would not result in preventing emails from being sent.

110:
Post Office Protocol (POP) is an email protocol that is used to download
email messages from a remote server. This could be the protocol the network clients are using to receive their email. POP uses port 110 by default. As this is a mail recovery protocol, and is not used for sending the emails,blocking this port will not provide the desired results.

143:
Internet Message Access Protocol (IMAP) is a more desirable mail retrieval protocol, by default it uses port 143. This protocol can access mail from an online server, but unlike POP which downloads the email from the server, IMAP leaves a copy on the mail server. This is useful if clients access email from multiple computers. As this is being used to retrieve email, blocking this protocol would not result in the desired outcome..

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