The following are common terms we use when describing email and how it moves between systems.

  • MTA – Mail Transfer Agent – the program that passes email between systems before it is
  • MUA – Mail User Agent, more commonly known as your Email Client (OE, Thunderbird, etc).
  • SMTP – The Simple Mail Transfer Protocol is how systems pass email between each other before it reaches the receiving user’s system
  • SMTP Envelope – The active parts of an SMTP conversation
  • Mail Headers – The
  • Mail Body – The actual content of the message