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Sender Policy Framework
Sender Policy Framework (SPF) is an email authentication method that ensures the sending mail server is authorized to originate mail from the email sender's domain. This authentication only applies to the email sender listed in the "envelope from" field during the initial SMTP connection. If the email is bounced, a message is sent to this address, and for downstream transmission it typically appears in the "Return-Path" header. To authenticate the email address which is actually visible to recipients on the "From:" line, other technologies, such as DMARC, must be used. Forgery of this address is known as email spoofing, and is often used in phishing and email spam. The list of authorized sending hosts and IP addresses for a domain is published in the DNS records for that domain. Sender Policy Framework is defined in RFC 7208 dated April 2014 as a "proposed standard". History The first public mention of the concept was in 2000 but went mostly unnoticed. No mention was made of th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Email Authentication
Email authentication, or validation, is a collection of techniques aimed at providing verifiable information about the origin of email messages by validating the Domain name#Purpose, domain ownership of any message transfer agents (MTA) who participated in transferring and possibly modifying a message. The original base of Internet email, Simple Mail Transfer Protocol (SMTP), has no such feature, so forged sender addresses in emails (a practice known as email spoofing) have been widely used in phishing, email spam, and various types of frauds. To combat this, many competing email authentication proposals have been developed. three had been widely adopted – Sender Policy Framework, SPF, DKIM and DMARC. The results of such validation can be used in automated email filtering, or can assist recipients when selecting an appropriate action. This article does not cover user authentication of email submission and retrieval. Rationale In the early 1980s, when Simple Mail Transfer Protoc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
E-mail Spam
Email spam, also referred to as junk email, spam mail, or simply spam, refers to unsolicited messages sent in bulk via email. The term originates from a Monty Python sketch, where the name of a canned meat product, "Spam," is used repetitively, mirroring the intrusive nature of unwanted emails. Since the early 1990s, spam has grown significantly, with estimates suggesting that by 2014, it comprised around 90% of all global email traffic. Spam is primarily a financial burden for the recipient, who may be required to manage, filter, or delete these unwanted messages. Since the expense of spam is mostly borne by the recipient, it is effectively a form of " postage due" advertising, where the recipient bears the cost of unsolicited messages. This cost imposed on recipients, without compensation from the sender, makes spam an example of a " negative externality" (a side effect of an activity that affects others who are not involved in the decision). The legal definition and status of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bounce Message
A bounce message or just "bounce" is an automated message from an email system, informing the sender of a previous message that the message has not been delivered (or some other delivery problem occurred). The original message is said to have "bounced". This feedback may be immediate (some of the causes described here) or, if the sending system can retry, may arrive days later after these retries end. More formal terms for bounce message include "Non-Delivery Report" or "Non-Delivery Receipt" (NDR), ailed"Delivery Status Notification" (DSN) message, or a "Non-Delivery Notification" (NDN). Classification Although the SMTP is a mature technology, counting more than thirty years, its architecture is increasingly strained by both normal and unsolicited load. The email systems have been enhanced with reputation systems tied to the actual sender of the email, with the idea of recipient's email servers rejecting the email when a forged sender is used in the protocol. Therefore, t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mail Transfer Agent
Within the Internet email system, a message transfer agent (MTA), mail transfer agent, or mail relay is software that transfers electronic mail messages from one computer to another using the Simple Mail Transfer Protocol. In some contexts, the alternative names mail server, mail exchanger, or MX host are used to describe an MTA. Messages exchanged across networks are passed between mail servers, including any attached data files (such as images, multimedia, or documents). These servers often keep mailboxes for email. Access to this email by end users is typically either by webmail or an email client. Operation A message transfer agent receives mail from either another MTA, a mail submission agent (MSA), or a mail user agent (MUA). The transmission details are specified by the Simple Mail Transfer Protocol (SMTP). When a recipient mailbox of a message is not hosted locally, the message is relayed, that is, forwarded to another MTA. Every time an MTA receives an email message, i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Return-Path
{{Redir, Return path, the term in electronics, Return path (electronics) A bounce address is an email address to which bounce messages are delivered. There are many variants of the name, none of them used universally, including return path, reverse path, envelope from, envelope sender, MAIL FROM, 5321-FROM, return address, From_, Errors-to, etc. It is not uncommon for a single document to use several of these names. All of these names refer to the email address provided with the MAIL FROM command during the SMTP session. Background information Ordinarily, the bounce address is not seen by email users and, without standardization of the name, it may cause confusion. If an email message is thought of as resembling a traditional paper letter in an envelope, then the "header fields", such as To:, From:, and Subject:, along with the body of the message are analogous to the letterhead and body of a letter - and are normally all presented and visible to the user. However, the envelo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Email Forwarding
Email forwarding generically refers to the operation of re-sending a previously delivered email to an email address to one or more different email addresses. The term ''forwarding'', used for mail since long before electronic communications, has no specific technical meaning,In section 3.9.2 ''List'' of RFC 5321, the term ''forwarding'' is used ambiguously. It notes that "''the key difference between handling aliases (Section 3.9.1) and forwarding (this subsection) is the change to the 'Return-Path'' header'." That wording, new w.r.t. RFC 2821, could be interpreted as the definition of ''forwarding'', if the same term weren't used at the beginning of the same subsection with the opposite meaning. As a contributor to RFC 5321 agreed, but it implies that the email has been moved "forward" to a new destination. Email forwarding can also redirect mail going to a certain address and send it to one or more other addresses. Vice versa, email items going to several different addresses ca ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Backscatter (e-mail)
Backscatter (also known as outscatter, misdirected bounces, blowback or collateral spam) is incorrectly automated bounce messages sent by mail servers, typically as a side effect of incoming spam. Recipients of such messages see them as a form of unsolicited bulk email or spam, because they were not solicited by the recipients. They are substantially similar to each other, and are delivered in bulk quantities. Systems that generate email backscatter may be listed on various email blacklists and may be in violation of internet service providers' terms of service. Backscatter occurs because worms and spam messages often forge their sender addresses. Instead of simply rejecting a spam message, a misconfigured mail server sends a bounce message to such a forged address. This normally happens when a mail server is configured to relay a message to an after-queue processing step, for example, an antivirus scan or spam check, which then fails, and at the time the antivirus scan or ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bounce Message
A bounce message or just "bounce" is an automated message from an email system, informing the sender of a previous message that the message has not been delivered (or some other delivery problem occurred). The original message is said to have "bounced". This feedback may be immediate (some of the causes described here) or, if the sending system can retry, may arrive days later after these retries end. More formal terms for bounce message include "Non-Delivery Report" or "Non-Delivery Receipt" (NDR), ailed"Delivery Status Notification" (DSN) message, or a "Non-Delivery Notification" (NDN). Classification Although the SMTP is a mature technology, counting more than thirty years, its architecture is increasingly strained by both normal and unsolicited load. The email systems have been enhanced with reputation systems tied to the actual sender of the email, with the idea of recipient's email servers rejecting the email when a forged sender is used in the protocol. Therefore, t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Message Transfer Agent
Within the Internet email system, a message transfer agent (MTA), mail transfer agent, or mail relay is software that transfers electronic mail messages from one computer to another using the Simple Mail Transfer Protocol. In some contexts, the alternative names mail server, mail exchanger, or MX host are used to describe an MTA. Messages exchanged across networks are passed between mail servers, including any attached data files (such as images, multimedia, or documents). These servers often keep mailboxes for email. Access to this email by end users is typically either by webmail or an email client. Operation A message transfer agent receives mail from either another MTA, a mail submission agent (MSA), or a mail user agent (MUA). The transmission details are specified by the Simple Mail Transfer Protocol (SMTP). When a recipient mailbox of a message is not hosted locally, the message is relayed, that is, forwarded to another MTA. Every time an MTA receives an email message, it ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Client (computing)
is a computer that gets information from another computer called server in the context of client–server model of computer networks. The server is often (but not always) on another computer system, in which case the client accesses the service by way of a network. A client is a program that, as part of its operation, relies on sending a request to another program or a computer hardware or software that accesses a service made available by a server (which may or may not be located on another computer). For example, web browsers are clients that connect to web servers and retrieve web pages for display. Email clients retrieve email from mail servers. Online chat uses a variety of clients, which vary on the chat protocol being used. Multiplayer video games or online video games may run as a client on each computer. The term "client" may also be applied to computers or devices that run the client software or users that use the client software. A client is part of a cl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Server (computing)
A server is a computer that provides information to other computers called " clients" on a computer network. This architecture is called the client–server model. Servers can provide various functionalities, often called "services", such as sharing data or resources among multiple clients or performing computations for a client. A single server can serve multiple clients, and a single client can use multiple servers. A client process may run on the same device or may connect over a network to a server on a different device. Typical servers are database servers, file servers, mail servers, print servers, web servers, game servers, and application servers. Client–server systems are usually most frequently implemented by (and often identified with) the request–response model: a client sends a request to the server, which performs some action and sends a response back to the client, typically with a result or acknowledgment. Designating a computer as "server-class hardwa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DNSBL
A Domain Name System blocklist, Domain Name System-based blackhole list, Domain Name System blacklist (DNSBL) or real-time blackhole list (RBL) is a service for operation of mail servers to perform a check via a Domain Name System (DNS) query whether a sending host's IP address is blacklisted for email spam. Most mail server software can be configured to check such lists, typically rejecting or flagging messages from such sites. A DNSBL is a software mechanism, rather than a specific list or policy. Dozens of DNSBLs exist. They use a wide array of criteria for listing and delisting addresses. These may include listing the addresses of zombie computers or other machines being used to send spam, Internet service providers (ISPs) who willingly host spammers, or those which have sent spam to a honeypot system. Since the creation of the first DNSBL in 1998, the operation and policies of these lists have frequently been controversial, both in Internet advocacy circles and occasion ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
