Unlike POP3 and IMAP that operate over ports 110 and 143, respectively, SMTP is a server-to-server protocol.Ĭlients use POP3 or IMAP to retrieve or send messages to the SMTP server, while the SMTP server then communicates to other SMTP servers.The SMTP server, obviously, maintains a database of every email address in the organization that it must send and receive email for. In this way, they are more likely to click on a link or open a document that we send them.There are multiple ways of collecting email addresses including, an email harvester, and others, but what if we could go directly into the organization's SMTP server and ask it if an email address exits? Wouldn't that be best and most reliable method? Background on SMTPAs you know, SMTP stands for Simple Mail Transport Protocol and operates on port 25. By having the email addresses of people within an organization, we can tailor our social engineering attack to particular people and circumstances within that organization (e.g., a sales report to the sales department) and maybe spoof the email address of a colleague within the organization.

Welcome back, my budding hackers!If we are considering a against a target, we are probably going to need email addresses.