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Greylisting (email)
Greylisting is a method of defending e-mail users against spam. A mail transfer agent (MTA) using greylisting will "temporarily reject" any email from a sender it does not recognize. If the mail is legitimate, the originating server will try again after a delay, and if sufficient time has elapsed, the email will be accepted. How it works A server employing greylisting temporarily rejects email from unknown or suspicious sources by sending 4xx reply codes ("please call back later"), as defined in the Simple Mail Transfer Protocol (SMTP). Fully capable SMTP implementations are expected to maintain queues for retrying message transmissions in such cases, and so while legitimate mail may be delayed, it should still get through. The temporary rejection can be issued at different stages of the SMTP dialogue, allowing an implementation to store more or less data about the incoming message. The trade-off is more work and bandwidth for more exact matching of retries with original messages. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
E-mail
Electronic mail (email or e-mail) is a method of exchanging messages ("mail") between people using electronic devices. Email was thus conceived as the electronic ( digital) version of, or counterpart to, mail, at a time when "mail" meant only physical mail (hence '' e- + mail''). Email later became a ubiquitous (very widely used) communication medium, to the point that in current use, an email address is often treated as a basic and necessary part of many processes in business, commerce, government, education, entertainment, and other spheres of daily life in most countries. ''Email'' is the medium, and each message sent therewith is also called an ''email.'' The term is a mass noun. Email operates across computer networks, primarily the Internet, and also local area networks. Today's email systems are based on a store-and-forward model. Email servers accept, forward, deliver, and store messages. Neither the users nor their computers are required to be online simult ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Postfix (software)
Postfix is a free and open-source mail transfer agent (MTA) that routes and delivers electronic mail. It is released under the IBM Public License 1.0 which is a free software license. Alternatively, starting with version 3.2.5, it is available under the Eclipse Public License 2.0 at the user's option. Originally written in 1997 by Wietse Venema at the IBM Thomas J. Watson Research Center in New York, and first released in December 1998, Postfix continues to be actively developed by its creator and other contributors. The software is also known by its former names VMailer and IBM Secure Mailer. The name Postfix is a compound of "post" (which is another word for "mail") and "fix "(which is for other software that inspired Postfix development). In a study published on June 1, 2022 by E-Soft, Inc., approximately 34% of the publicly reachable mail-servers on the Internet ran Postfix, making it the second most popular mail server behind Exim. Note: this survey covers less than 25% ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bandwidth Throttling
Bandwidth throttling consists in the intentional limitation of the communication speed (bytes or kilobytes per second) of the ingoing (received) data and/or in the limitation of the speed of outgoing (sent) data in a network node or in a network device. The data speed and rendering may be limited depending on various parameters and conditions. Overview Limiting the speed of data sent by a data originator (a client computer or a server computer) is much more efficient than limiting the speed in an intermediate network device between client and server because while in the first case usually no network packets are lost, in the second case network packets can be lost / discarded whenever ingoing data speed overcomes the bandwidth limit or the capacity of device and data packets cannot be temporarily stored in a buffer queue (because it is full or it does not exist); the usage of such a buffer queue is to absorb the peaks of incoming data for very short time lapse. In the second cas ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nolisting
Nolisting is the name given to a technique to defend electronic mail domain names against e-mail spam. Feb 2007, M Edwards, Windows IT Pro"Nolisting: Poor Man's Greylisting" /ref> Each domain name on the internet has a series of one or more s specifying mail servers responsible for accepting email messages on behalf of that domain, each with a preference. Nolisting is simply the adding of an MX record pointing to a non-existent server as the "primary" (i.e. that with the lowest weighted value) - which means that an init ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
IPv6
Internet Protocol version 6 (IPv6) is the most recent version of the Internet Protocol (IP), the communication protocol, communications protocol that provides an identification and location system for computers on networks and routes traffic across the Internet. IPv6 was developed by the Internet Engineering Task Force (IETF) to deal with the long-anticipated problem of IPv4 address exhaustion, and is intended to replace IPv4. In December 1998, IPv6 became a Draft Standard for the IETF, which subsequently ratified it as an Internet Standard on 14 July 2017. Devices on the Internet are assigned a unique IP address for identification and location definition. With the rapid growth of the Internet after commercialization in the 1990s, it became evident that far more addresses would be needed to connect devices than the IPv4 address space had available. By 1998, the IETF had formalized the successor protocol. IPv6 uses 128-bit addresses, theoretically allowing 2128, or approximatel ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DHCP
The Dynamic Host Configuration Protocol (DHCP) is a network management protocol used on Internet Protocol (IP) networks for automatically assigning IP addresses and other communication parameters to devices connected to the network using a client–server architecture. The technology eliminates the need for individually configuring network devices manually, and consists of two network components, a centrally installed network DHCP server and client instances of the protocol stack on each computer or device. When connected to the network, and periodically thereafter, a client requests a set of parameters from the server using DHCP. DHCP can be implemented on networks ranging in size from residential networks to large campus networks and regional ISP networks. Many routers and residential gateways have DHCP server capability. Most residential network routers receive a unique IP address within the ISP network. Within a local network, a DHCP server assigns a local IP address to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Link Aggregation
In computer networking, link aggregation is the combining ( aggregating) of multiple network connections in parallel by any of several methods, in order to increase throughput beyond what a single connection could sustain, to provide redundancy in case one of the links should fail, or both. A link aggregation group (LAG) is the combined collection of physical ports. Other umbrella terms used to describe the concept include trunking, bundling, bonding, channeling or teaming. Implementation may follow vendor-independent standards such as Link Aggregation Control Protocol (LACP) for Ethernet, defined in IEEE 802.1AX or the previous IEEE 802.3ad, but also proprietary protocols. Motivation Link aggregation increases the bandwidth and resilience of Ethernet connections. Bandwidth requirements do not scale linearly. Ethernet bandwidths historically have increased tenfold each generation: 10 megabit/s, 100 Mbit/s, 1000 Mbit/s, 10,000 Mbit/s. If one started to bump in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mail Transfer Agent
The mail or post is a system for physically transporting postcards, letters, and parcels. A postal service can be private or public, though many governments place restrictions on private systems. Since the mid-19th century, national postal systems have generally been established as a government monopoly, with a fee on the article prepaid. Proof of payment is usually in the form of an adhesive postage stamp, but a postage meter is also used for bulk mailing. With the advent of email, the retronym "snail mail" was coined. Postal authorities often have functions aside from transporting letters. In some countries, a postal, telegraph and telephone (PTT) service oversees the postal system, in addition to telephone and telegraph systems. Some countries' postal systems allow for savings accounts and handle applications for passports. The Universal Postal Union (UPU), established in 1874, includes 192 member countries and sets the rules for international mail exchanges as a Specialize ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Whitelist
A whitelist, allowlist, or passlist is a mechanism which explicitly allows some identified entities to access a particular privilege, service, mobility, or recognition i.e. it is a list of things allowed when everything is denied by default. It is the opposite of a blacklist, which is a list of things denied when everything is allowed by default. Email whitelists Spam filters often include the ability to "whitelist" certain sender IP addresses, email addresses or domain names to protect their email from being rejected or sent to a junk mail folder. These can be manually maintained by the user or system administrator - but can also refer to externally maintained whitelist services. Non-commercial whitelists Non-commercial whitelists are operated by various non-profit organisations, ISPs, and others interested in blocking spam. Rather than paying fees, the sender must pass a series of tests; for example, their email server must not be an open relay and have a static IP address. The ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Message Systems Momentum
A message is a discrete unit of communication intended by the source for consumption by some recipient or group of recipients. A message may be delivered by various means, including courier, telegraphy, carrier pigeon and electronic bus. A message can be the content of a broadcast. An interactive exchange of messages forms a conversation. One example of a message is a press release, which may vary from a brief report or statement released by a public agency to commercial publicity material. History Roles in human communication In communication between humans, messages can be verbal or nonverbal: * A verbal message is an exchange of information using words. Examples include face-to-face communication, telephone calls, voicemails, email etc. * A nonverbal message is communicated through actions or behaviors rather than words, such as conscious or unconscious body language. In computer science There are two main senses of the word "message" in computing: messages be ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Microsoft Exchange Server
Microsoft Exchange Server is a mail server and calendaring server developed by Microsoft. It runs exclusively on Windows Server operating systems. The first version was called Exchange Server 4.0, to position it as the successor to the related Microsoft Mail 3.5. Exchange initially used the X.400 directory service but switched to Active Directory later. Until version 5.0, it came bundled with an email client called Microsoft Exchange Client. This was discontinued in favor of Microsoft Outlook. Exchange Server primarily uses a proprietary protocol called MAPI to talk to email clients, but subsequently added support for POP3, IMAP, and EAS. The standard SMTP protocol is used to communicate to other Internet mail servers. Exchange Server is licensed both as on-premises software and software as a service (SaaS). In the on-premises form, customers purchase client access licenses (CALs); as SaaS, Microsoft charges a monthly service fee instead. History Microsoft had sold a numbe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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