The heart of MailMan is a CGI application written in Perl,
version 5.  The mail application generates MailMan’s user
interface dynamically by reading template files filled with
HTML code, processing them, and producing output for the
user through a web server.  To obtain useful email
information, MailMan obtains a user’s email account
authentication information directly from the user (a
username, password and server name) and communicates with
the user’s POP3 email server the way that any client-side
mail software ordinarily would.  The user sees a list of
messages and can select messages for viewing, deletion, and
other normal mail tasks.  If a user wishes to reply to a
message, forward a message, or create a new message, MailMan
communicates with an SMTP mail server to send the outgoing
message the way that any ordinary client-side software
would.