An email passes through multiple servers that help ensure it arrives au right place. That email message flow uses a systematic process based on a number of long-established technical standards.
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Comprendre le flux des messages électroniques, de l'envoi à la livraison
For most users, how an email message flows from the sender to a recipient’s inbox is something that happens behind the scenes. When an individual or an organization sends an email, the message travels from its point of origination, such as an email client where it was composed, across the Internet to its destination. Along the way, it passes through multiple servers that help ensure it arrives at the right place. That email message flow uses a systematic process based on a number of long-established technical standards.
Comment se déroule un message électronique ?
Email has been around since the 1960s, when the creators of nascent computer networks began devising ways to send messages to each other. In those early days, users were limited to communicating only with others on the same shared mainframe system. However, the adoption of standard protocols and the interconnection of systems into the shared network we now know as the Internet allowed different mail systems to “talk” to each other.
It’s these standards that allow us to send email messages to virtually anyone. When someone sends an email message, it flows through a series of steps to reach its destination.
Lorsqu'une personne rédige un message, elle le fait généralement dans un client de messagerie tel qu'Outlook ou Apple Mail, ou dans un service en ligne tel que Gmail.
However, when the message is a courriel transactionnel like a shipping notice or a password reset, the message is created automatically by those systems, usually using an email API. (Marketing messages are generated by automated systems as well, although usually in large batches, rather than one at a time like transactional messages.)
In both cases, whether the message is created by an email client or by an automated system, it is specially formatted to be transmitted over the Internet using a standard called “Simple Mail Transfer Protocol” (SMTP).
Le sender’s mail server (technically called a “Mail Transfer Agent,” or MTA) looks up the “@domain.com” portion of the recipient’s email address in a Domain Name System (DNS) server to determine which destination mail server (referred to as a “Mail Exchanger,” or MX) it should contact to deliver the message.
Le sending and receiving servers communicate using the SMTP protocol. The receiving server accepts the message so that it can be delivered to the recipient.
The recipient’s email client retrieves the message using standards like the Post Office Protocol (POP) or Internet Message Access Protocol (IMAP) to download the message so it can be read.
Comment les clients de messagerie téléchargent-ils un message ?
Web-based email services like Gmail or Hotmail/Outlook.com use their own internal protocols to manage email. But when recipients use a stand-alone email client on a phone or desktop computer, that software uses standard protocols to download messages from mail servers.
Lorsque le destinataire utilise le protocole POP, le serveur lui remet tous les nouveaux messages électroniques et n'en conserve des copies que si une option du client de messagerie est cochée, le cas échéant. Si le serveur n'a pas de copies des messages électroniques et que le destinataire subit une perte ou une panne de matériel, ces messages disparaissent à jamais, à moins que les expéditeurs n'en aient des copies.
Lorsque le destinataire utilise le protocole IMAP, le serveur synchronise le contenu de la boîte aux lettres, y compris les éléments envoyés et les autres dossiers, avec chaque appareil qui s'y connecte. Les messages restent sur le serveur et lorsque l'état de l'un d'entre eux change (par exemple, il est lu ou supprimé), ce changement se propage sur tous les appareils lorsqu'ils se connectent à nouveau.
La possibilité de conserver et de synchroniser les messages sur plusieurs appareils est la raison pour laquelle la plupart des services de messagerie électronique utilisent aujourd'hui le protocole IMAP plutôt que le protocole POP.
En savoir plus sur le flux de messages électroniques
Email involves many different steps and systems. You can learn more about the inner workings of email delivery with these resources:
Email: This Wikipedia article delves into the history of email as well as its many technical details. It links out to several supporting articles that flesh out the main subject.
Email API: Learn more about how e-commerce and other systems can generate transactional email very efficiently.
Livraison d'e-mails dans le nuage: Learn more about how systems the SparkPost email delivery service work to make large-scale email transmission and delivery practical.