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Message Submission Agent
A message submission agent (MSA), or mail submission agent, is a computer program or software agent that receives electronic mail messages from a mail user agent (MUA) and cooperates with a mail transfer agent (MTA) for delivery of the mail. It uses ESMTP, a variant of the Simple Mail Transfer Protocol (SMTP), as specified in RFC 6409. Many MTAs perform the function of an MSA as well, but there are also programs that are specially designed as MSAs without full MTA functionality. Historically, in Internet mail, both MTA and MSA functions use port number 25, but the official port for MSAs is 587. The MTA accepts a user's incoming mail, while the MSA accepts a user's outgoing mail. Benefits Separation of the MTA and MSA functions produces several benefits. One benefit is that an MSA, since it is interacting directly with the author's MUA, can correct minor errors in a message's format (such as a missing ''Date'', ''Message-ID'', ''To'' fields, or an address with a missing domain ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Computer Program
A computer program is a sequence or set of instructions in a programming language for a computer to execute. Computer programs are one component of software, which also includes documentation and other intangible components. A computer program in its human-readable form is called source code. Source code needs another computer program to execute because computers can only execute their native machine instructions. Therefore, source code may be translated to machine instructions using the language's compiler. ( Assembly language programs are translated using an assembler.) The resulting file is called an executable. Alternatively, source code may execute within the language's interpreter. If the executable is requested for execution, then the operating system loads it into memory and starts a process. The central processing unit will soon switch to this process so it can fetch, decode, and then execute each machine instruction. If the source code is requested for execution, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Author Domain Signing Practices
In computing, Author Domain Signing Practices (ADSP) is an optional extension to the DKIM E-mail authentication scheme, whereby a domain can publish the signing practices it adopts when relaying mail on behalf of associated authors. ADSP was adopted as a standards track RFC 5617 in August 2009, but declared "Historic" in November 2013 after "...almost no deployment and use in the 4 years since...". Concepts Author address The ''author address'' is the one specified in the header field defined in RFC 5322. In the unusual cases where more than one address is defined in that field, RFC 5322 provides for a field to be used instead. The domains in 5322-''From'' addresses are not necessarily the same as in the more elaborated ''Purported Responsible Address'' covered by Sender ID specified in RFC 4407. The domain in a 5322-''From'' address is also not necessarily the same as in the ''envelope sender'' address defined in RFC 5321, also known as SMTP MAIL FROM, envelope-''From'', ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Comparison Of Mail Servers
The comparison of mail servers covers mail transfer agents (MTAs), mail delivery agents, and other computer software that provide e-mail services. Unix-based mail servers are built using a number of components because a Unix-style environment is, by default, a toolbox operating system. A stock Unix-like server already has internal mail; more traditional ones also come with a full MTA already part of the standard installation. To allow the server to send external emails, an MTA such as Sendmail, Postfix, or Exim is required. Mail is read either through direct access (shell login) or mailbox protocols like POP and IMAP. Unix-based MTA software largely acts to enhance or replace the respective system's native MTA. Microsoft Windows servers do not natively implement e-mail, thus Windows-based MTAs have to supply all the necessary aspects of e-mail-related functionality. Feature comparison Authentication Antispam features See also * Comparison of email clients * Li ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
List Of Mail Servers
This is a list of mail server software: mail transfer agents, mail delivery agents, and other computer software which provide e-mail. Product statistics All such figures are necessarily estimates because data about mail server share is difficult to obtain; there are few reliable primary sources—and no agreed methodologies for its collection. Surveys probing Internet-exposed systems typically attempt to identify systems via their banner, or other identifying features; and report Postfix and exim as overwhelming leaders in March 2021, with greater than 92% share between them. SMTP POP/IMAP Mail filtering Mail server packages * Mail-in-a-Box * iRedmail * Modoboa * Mailcowhttps://mailcow.email/ See also * Comparison of mail servers * Message transfer agent Within the Internet email system, a message transfer agent (MTA), or mail transfer agent, or mail relay is software that transfers electronic mail messages from one computer to another using SMTP. The terms mail ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
E-mail 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 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 fraud. To combat this, many competing email authentication proposals have been developed, but only fairly recently have three been widely adopted – 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 Protocol (SMTP) was design ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sender ID
Sender ID is an historic anti- spoofing proposal from the former MARID IETF working group that tried to join Sender Policy Framework (SPF) and Caller ID. Sender ID is defined primarily in Experimental RFC 4406, but there are additional parts in RFC 4405, RFC 4407 and RFC 4408. Principles of operation Sender ID is heavily based on SPF, with only a few additions. Sender ID tries to improve on SPF: SPF does not verify the header addresses (of which there can be more than one) that indicate the claimed sending party. One of these header addresses is typically displayed to the user and may be used to reply to emails. These header addresses can be different from the address that SPF tries to verify; that is, SPF verifies only the "MAIL FROM" address, also called the envelope sender. However, there are many similar email header fields that all contain sending party information; therefore Sender ID defines in RFC 4407 a Purported Responsible Address (PRA) as well as a set of heuristi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sender Policy Framework
Sender Policy Framework (SPF) is an email authentication method designed to detect forging sender addresses during the delivery of the email. SPF alone, though, is limited to detecting a forged sender claim in the envelope of the email, which is used when the mail gets bounced. Only in combination with DMARC can it be used to detect the forging of the visible sender in emails (email spoofing), a technique often used in phishing and email spam. SPF allows the receiving mail server to check during mail delivery that a mail claiming to come from a specific domain is submitted by an IP address authorized by that domain's administrators. 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 the concept again until a first att ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bounce Address
{{No footnotes, date=June 2016 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 envelope in this analogy is the contents of the M ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
POP Before SMTP
POP before SMTP or SMTP after POP is a method of authentication used by mail server software which helps allow users the option to send e-mail from any location, as long as they can demonstrably also fetch their mail from the same place. The POP before SMTP approach has been superseded by SMTP Authentication. Technically, users are allowed to use SMTP from an IP address as long as they have previously made a successful login into the POP service at the same mail hosting provider, from the same address, within a predefined timeout period. The main advantage of this process is that it was generally transparent to the average user who will be connecting with an email client, which almost always attempted to fetch new mail before sending new mail. The disadvantages include a potentially complex setup for the mail hosting provider (requiring some sort of communication channel between the POP service and the SMTP service) and uncertainty as to how much time users will take to connect ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Public Key Certificate
In cryptography, a public key certificate, also known as a digital certificate or identity certificate, is an electronic document used to prove the validity of a public key. The certificate includes information about the key, information about the identity of its owner (called the subject), and the digital signature of an entity that has verified the certificate's contents (called the issuer). If the signature is valid, and the software examining the certificate trusts the issuer, then it can use that key to communicate securely with the certificate's subject. In email encryption, code signing, and e-signature systems, a certificate's subject is typically a person or organization. However, in Transport Layer Security (TLS) a certificate's subject is typically a computer or other device, though TLS certificates may identify organizations or individuals in addition to their core role in identifying devices. TLS, sometimes called by its older name Secure Sockets Layer (SSL), is notable ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
RADIUS
In classical geometry, a radius ( : radii) of a circle or sphere is any of the line segments from its center to its perimeter, and in more modern usage, it is also their length. The name comes from the latin ''radius'', meaning ray but also the spoke of a chariot wheel. as a function of axial position ../nowiki>" Spherical coordinates In a spherical coordinate system, the radius describes the distance of a point from a fixed origin. Its position if further defined by the polar angle measured between the radial direction and a fixed zenith direction, and the azimuth angle, the angle between the orthogonal projection of the radial direction on a reference plane that passes through the origin and is orthogonal to the zenith, and a fixed reference direction in that plane. See also *Bend radius *Filling radius in Riemannian geometry *Radius of convergence * Radius of convexity *Radius of curvature *Radius of gyration ''Radius of gyration'' or gyradius of a body about the axis of r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
SRV Record
A Service record (SRV record) is a specification of data in the Domain Name System defining the location, i.e., the hostname and port number, of servers for specified services. It is defined iRFC 2782 and its type code is 33. Some Internet protocols such as the Session Initiation Protocol (SIP) and the Extensible Messaging and Presence Protocol (XMPP) often require SRV support by network elements. Record format A SRV record has the form: _service._proto.name. ttl IN SRV priority weight port target. * ''service'': the symbolic name of the desired service. * ''proto'': the transport protocol of the desired service; this is usually either TCP or UDP. * ''name'': the domain name for which this record is valid, ending in a dot. * ''ttl'': standard DNS time to live field. * ''IN'': standard DNS class field (this is always ''IN''). * ''SRV'': Type of Record (this is always ''SRV''). * ''priority'': the priority of the target host, lower value means more preferred. * ''weight'': A re ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
