An email passes through multiple servers that help ensure it arrives aan de right place. That email message flow uses a systematic process based on a number of long-established technical standards.
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E-mailberichtenstroom begrijpen, van verzenden tot afleveren
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.
Hoe verloopt een e-mailbericht?
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.
Wanneer iemand een bericht schrijft, gebeurt dat meestal in een e-mailprogramma zoals Outlook of Apple Mail, of in een webgebaseerde service zoals Gmail.
However, when the message is a transactionele e-mail 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).
De 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.
De 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.
Hoe downloaden e-mailclients een bericht?
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.
Als de ontvanger POP gebruikt, levert de server alle nieuwe e-mails bij hem af en bewaart alleen kopieën als een optie in de e-mailclient is aangevinkt, indien van toepassing. Als de server geen kopieën van de e-mails heeft en de ontvanger een hardwareverlies of -storing heeft, zijn die berichten voor altijd verdwenen, tenzij de afzenders er kopieën van hebben.
Wanneer de ontvanger IMAP gebruikt, synchroniseert de server de inhoud van de mailbox, inclusief de verzonden items en andere mappen, naar elk apparaat dat er verbinding mee maakt. De berichten blijven op de server en wanneer de status van een bericht verandert (bijvoorbeeld gelezen of verwijderd), wordt die verandering doorgevoerd op alle apparaten wanneer ze opnieuw verbinding maken.
De mogelijkheid om berichten op meerdere apparaten te bewaren en te synchroniseren is de reden waarom de meeste e-maildiensten tegenwoordig IMAP gebruiken in plaats van POP.
Meer lezen over e-mail berichtenstroom
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.
E-maillevering in de cloud: Learn more about how systems the SparkPost email delivery service work to make large-scale email transmission and delivery practical.