Even now, while many proprietary systems like Microsoft Exchange and webmail programs like Gmail use their own protocols internally, they use SMTP to transfer messages outside their systems for example, if a Gmail user wants to send an email to an Outlook client.
Mail would then be downloaded from the server using Post Office Protocol POP3 POP3 is an application-layer protocol which provides access via an internet protocol IP network for a user application to contact a mailbox on a mail server. It can connect, retrieve messages, store them on the client's computer, and delete or retain them on the server. It was designed to be able to manage temporary internet connections, such as dial-up so it would just connect and retrieve email when connected, and allow you to view the messages when you were offline.
This was more popular when dial-up access was more widespread. IMAP can allow multiple clients to manage the same mailbox so you can read your email from your desktop, laptop, and phone, etc. Eventually, webmail replaced both. Webmail allows you to login to a website and receive messages from anywhere or any device yay!
Unfortunately, security wasn't really built into mail protocols from the beginning like most beginning internet protocols. Servers just expected to take any message from anyone and pass it along to any other server which could help route the message to its final destination the recipient in the to: field. Unsurprisingly, this became an issue when the internet expanded from a few government and research groups into something most of the world uses to do essentially everything.
Pretty soon spam and phishing emails became and remain a huge problem for everyone. In response, we've collectively tried to implement several measures which prevent people from reading other's messages encryption and validate that messages actually came from the purported sender authentication.
Most places use TLS transport layer security, the replacement for SSL, secure sockets layer , a cryptographic protocol which provides encryption in transit. It provides protection for when the message is being transmitted, but not when the data is at rest, for example, being stored on your computer. However, this doesn't verify that the message wasn't modified during the trip. For example, if the email goes through multiple mail servers before it reaches its final destination, using TLS will ensure it is encrypted between the servers, but each server could alter the message content.
SPF allows the owner of a domain like google. In practice, this step is seldom necessary. The MTA can bypass this step because it has already knows which domain name servers handle requests for these. When is transferring messages, it is called an MTA. The sending MTA asks if the host accepts messages for the recipient's username at that domain i. The transfer process described in the last step is somewhat simplified.
An email may be transferred to more than one MTA within a network cloud and is likely to be passed to at least one firewall before it reaches it's destination. An email encountering a firewall may be tested by spam and virus filters before it is allowed to pass inside the firewall.
These filters test to see if the message qualifies as spam or malware. If the message contains malware, the file is usually quarantined and the sender is notified. If the message is identified as spam, it will probably be deleted without notifying the sender.
Spam is difficult to detect because it can assume so many different forms, so spam filters test on a broad set of criteria and tend to misclassify a significant number of messages as spam, particularly messages from mailing lists. When an email from a list or other automated source seems to have vanished somewhere in the network cloud, the culprit is usually a spam filter at the receiver's ISP or company.
This explained in greater detail in Virus Scanning and Spam Blocking. In the diagram, the email makes it past the hazards of the spam trap There are many RFCs and they form a somewhat complex, interlocking set of standards, but they are a font of information for anyone interested in gaining a deeper understanding of email.
Email construction and delivery is similar to regular mail by design, because email is modeled on regular mail. An email message is constructed like a letter you'd send through the postal service: a message enclosed in an envelope.
The email envelope header is analogous to the envelope of a hardcopy letter, but some of the information that is ordinarily present on a hardcopy envelope is contained in the message header instead of the envelope header. This header header also contains information that is not usually found on a real-world envelope, but is essential to email delivery and troubleshooting.
The envelope header is usually hidden when you view an email, and the message header is usually visible.
Together, these two headers are called the full header. Anyone who has used email is familiar with the message header, which is displayed when you view an email message and includes the 'From:', 'To:', 'Cc:', 'Date:' and 'Subject:' fields.
The content of these fields differs only slightly from regular mail, because the 'From:', 'To:' and 'Cc:', fields in an email identify the sender and intended recipients by email address. Published: Jun 30, Comments: 2. Did you find this article helpful? Why was this article not helpful? Check all that apply. Next ». Help Center Login Login with Facebook. Creating an Email Account 3. How to Check your Email 4. Related Questions Here are a few questions related to this article that our customers have asked:.
It looks like there are no questions about this page. If you're online a lot, you yourself may send a dozen or more emails each day without even thinking about it. Obviously, email has become an extremely popular communication tool.
Have you ever wondered how email gets from your computer to a friend halfway around the world? What is a POP3 server, and how does it hold your mail? The answers may surprise you, because it turns out that email is an incredibly simple system at its core.
In this article, we'll take an in-depth look at email and how it works. According to Darwin Magazine: Prime Movers, the first email message was sent in by an engineer named Ray Tomlinson.
Before this, you could only send messages to users on a single machine. Tomlinson's breakthrough was the ability to send messages to other machines on the Internet, using the sign to designate the receiving machine.
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