2.3 Email Flashcards
the 3 major components of email
- user agent
- mail client
- SMTP protocol
user agent definition
the mail client you use (Outlook, Gmail)
for writing, editing, reading messages
mail server definition
stores incoming/outgoing messages
the “mailbox”
contains message queue (mail waiting to be sent to SMTP)
SMTP definition
Simple Mail Transfer Protocol
protocol between mail servers that sends emails
operates on top of TCP, using it to reliably transfer emails from client to server
the process of sending email example (Alice –> Bob)
Alice’s email client –> Alice’s mail server (SMTP)
Alice’s mail server –> Bob’s mail server (SMTP)
Bob’s mail server –> Bob’s email client (POP3, IMAP, or HTTP)
What does RFC 5321 define?
SMTP protocol
port 25 meaning
the standard server port number associated with SMTP
this way, the client always knows the port number on which to contact the SMTP server
the 3 phases of message transfer
- SMTP handshaking
- SMTP transfer of messages
- SMTP closure (TCP is closed)
the 3 mail access protocols (the protocols that retrieve mail)
IMAP (Internet Mail Access Protocol) = a mail access protocol with features that manipulate the emails that are stored on the server (retrieval, deletion, folders)
HTTP (Hypertext Transfer Protocol) = retrieves an email message from a web server that is also configured to return email messages
Gmail, Outlook, Yahoo
POP3 (Post Office Protocol) = a pull protocol used by email clients to retrieve emails from a server,
for single-device use (emails are downloaded to ONE device and automatically deleted from the server)
push and pull protocols meaning
push protocol - requesting data
pull protocol - receiving data
command-response interaction meaning
one device (the client) sends a command
the other device (the server) processes it and sends back a response
What service runs on port 25?
SMTP
What type of identifier is used for a socket?
port number
