Email is a shorthand term which means: electronic mail. Email is similar to a regular postal letter; containing an address, routing information and content. Email uses a range of protocol's - like IMAP, POP3, SMTP - to route messages from mail servers to users. Email - as a technology - predates the Internet, and was first implemented in ARPANET (1972).
Email, as a term, can also be written as: e-mail. To send and receive email messages a user requires an email address. The majority of Internet Service Provider provide a free email account to customers; likewise, there are a plethora of companies who provide free webmail accounts, such as: Gmail and Yahoo!. Email client programs (like Outlook Express) can be used to access an email account.
Email has proved to be one of the Internet's most popular services; while it has been commended for improving global communications, it has also be criticised for it's security: spam, and viruses and malware being spread through email attachments.
The history of email predates the modern day Internet: Email was created for the ARPANET computer network in the 1970's. It is generally believed that email grew out of the Mail Box Protocol, and Ray Tomlinson is created as it's inventor (1972). ARPANET was a forerunner to the modern day Internet; ARPANET used a similar network architecture to the Internet, therefore, email made a seamless transition to the Internet.
While email was created for ARPANET in the early 1970's, digital messaging is far order. In 1966, MIT developed the CTSS computer system, and this computer system featured a messaging system similar to Email. However, CTSS was not the only computer system that featured one-to-one messaging in the 1960's.
Email was immediately popular with ARPANET users, and many Internet pioneers had a 'hand' in it's development: such as Jon Postel, Larry Roberts and John Vittal. Intially, email was used by academic researchers and the military. Only by the 1980's did ordinary people begin to use email, and by the 1990's - when commercial networks controlled the backbone of the Internet - it had become the Internet's most popular service.
As stated, email grew out of the Mail Box Protocol: early email systems were highly reliant on the FTP protocol, and only at a late date were standalone protocols developed for email, such as: IMAP, X400, POP, SMTP, and UUCP. The most important protocol that was development for email was SMTP; SMTP was invented in the early 1980's and is still in use today (2015). POP was another important email protocol that was developed in the early 1980's, and IMAP was an email protocol developed in the mid 1980's by Mark Crispin. Some email protocols became obsolete: such as Jon Postel's Mail Transfer Protocol (MTP). Present day, most email systems rely on either: SMTP, POP or IMAP.
The key features of an email message have remained the same, comprising: a header and a body. The format of a email address has also remained the same: Ray Tomlinson being the inventor of using the @ symbol in 1972.
The format of email messages is broken into two sections: 1) a header, 2) message body. (read more on the header and body)
The header of an email message is more complex, and contains the information needed to encode and route the email message. The header can include multiple fields, but four popular fields are:: From:; To:; Cc:; and Subject:. The two fields which an email message must include are the From: and Date: fields.
The From: and To: fields are somewhat self explanatory (email address of the sender and receiver); the Cc: field is used to send a message to multiple additional addresses (Bcc: field hides the addresses from other recipients); the Subject: field is used to describe what is included in the body of the message.
Originally email messages were only plain text, and some mail servers will only support plain text email messages. However, if the content type of the email (included in the header) supports MIME: then the body of the email message can be encoded with HTML elements. Therefore, the body section of an email message can include plain text and HTML content.
The header section of an email message contains lines of instructions, which are sometimes referred to as "header identifiers". The primary role of these identifiers is to provide routing commands for mail transfer agents (which play the online role of a postal service). Some of these identifiers are mandatory for an email message; which basically means the email message cannot be sent without them: the following identifiers are mandatory,
Alongside the mandatory header identifier, there are a plethora of identifiers which deal with the cosmetic aspects of the email. Listed below, is the typical amount of identifiers you will find in an email header,
Email headers sometimes contain two or more of the same identifiers, usually the "received" and "date" identifiers: which are added to the header by each mail transfer agent that handles the message.
An e-mail address can be broken down into three section, coloured below:
The first section is the username (editor) which refers to the recipient's account name at a mail service; also referred to as the 'local' part of an email address. Secondly there is the @ sign - which is included in every email address - and means 'at' and connects the local part of the email address to the hostname of the email address.
Then comes the hostname (internet-guide), which can also be called
the domain name. This refers to the mail server address: usually
having an individual IP address. The hostname of an email address
can include a range of top-level domain names (TLD). For example,
'co.uk', is for commercial sites based in the United Kingdom.
When sending email messages, it is essential to spell the email address correctly; just as with a normal postal letter. If the email address is entered incorrectly, then it will not be sent to the correct person. If you send an email to an address which does not exist: then the message will be returned with an "Address Unknown" error.
E-mail's are transferred from one computer to another by a Mail transfer agent (MTA) (a mail server is a computer acting as a MTA). The 'Simple Mail Transfer Protocol' - abbreviated as SMTP - is the most popular protocol that MTAs use. Sendmail was the first MTA to use SMTP. You can learn more about the SMTP protocol by reading Request for Comments documents 'RFC 5322' and 'RFC 5321'. The 'Received' field in the e-mail header, is a list of the MTAs which have handled the e-mail.
After a MTA has transferred an e-mail, the message will usually reside on a remote server. The user will then retrieve the e-mail from an MTA using an e-mail client program (such as Outlook Express) (also called a mail reader or mail user agent (MUA)) or a webmail service (such as Gmail). Clients and webmail use a retrieval protocol such as IMAP or POP, to download the e-mail from an MTA to a client's inbox. (images, a picture of a client login and webmail login)
Once the e-mail has been retrieved, it then needs to be stored. There are many formats which can handle storage, perhaps the most simple and efficient is Maildir. Maildir operates by creating unique temporary files for each retrieved message; it will depend on the client or webmail, as to which storage format they will use. Maildir, for example, was designed for the qmail program, but is compatible with other clients. Not all storage formats create unique files for each e-mail; another option is to use a collective database format. mBox is one such example, storing messages in one single file. Why are there a variety of different techniques for storing messages? unlike message transfer, the Internet Engineering Task Force (IETF) has not developed a standard mechanism for storage.
E-mail process, step by step (sequence applies to most users)
Webmail, as the name would suggest, is an email service that is accessed through the World Wide Web. The World Wide Web was launched as an Internet service in 1991, whereas email was invented in the early 1970's. Therefore, webmail is a relatively new development for email; before webmail, most users accessed email through a standalone email client application, like Eudora. Webmail uses the same email protocols as earlier email clients, the only difference is the way in which the email account is accessed.
There are a plethora of free email accounts available from webmail providers, such as: hotmail. While early webmail services were criticised for a lack of protection versus email bombs, spam and flooding, modern webmail services provide protection against these abuses. Professional webmail services provide additional features, alongside the obvious features, such as: attachments, blind carbon copy options, e-cards, encryption and decryption. Every type of webmail account should be able to receive e-zines and newsletters.
The drawback with free webmail accounts is that the user cannot pick a unique domain name: instead they are stuck with domain name of the service provider: such as yahoo.com. However, user can pick an individual 'username' to suit their purposes. If a user wants an email address with a unique domain name - they can access the inbox with a client program - then they will have to purchase that domain name and host it with a company that provides support for email protocols.
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