# SendGrid Glossary ## A ### [Ad exchange](/docs/sendgrid/glossary/ad-exchange) *Advertising*. A digital marketplace where advertisers and publishers can buy and sell display, video, and mobile advertising. ### [Ad impression](/docs/sendgrid/glossary/ad-impression) *Advertising*. One occurence of an advertisement displaying on a screen. ### [Ad unit](/docs/sendgrid/glossary/ad-unit) *Advertising*. The container that holds the advertising copy and graphics for a digital advertisement on a screen. ### [Affiliate marketing](/docs/sendgrid/glossary/affiliate-marketing) *Marketing*. An activity in which companies offer to pay individuals or other businesses to promote their products or services. ### [Affirmative consent](/docs/sendgrid/glossary/affirmative-consent) *Reputation*. The informed, explicit acceptance that a recipient granted you to receive your email. ### [Allowlist](/docs/sendgrid/glossary/allow-list) *Internet Security*. A curated selection of domains, email addresses, or IP addresses that a service or system has granted explicit access. ### [Automated email](/docs/sendgrid/glossary/automated-email) *Marketing*. A system that allows the sending of messages with content relevant to individual recipients. ### [Autoresponder](/docs/sendgrid/glossary/autoresponder) *Marketing*. A system that generates email responses to actions and events. [Back to top](#top) ## B ### [Bayesian filter](/docs/sendgrid/glossary/bayesian-filter) *Email Deliverability*. A statistical technique that detects email spam. ### [Block](/docs/sendgrid/glossary/blocks) *Email Deliverability*. A temporary rejection of messages sent from your IP address. ### [Blocklist](/docs/sendgrid/glossary/blocklist) *Email Deliverability*. A list of IP addresses, email addresses, or domains known to ISPs or list providers for sending unsolicited or unwanted emails. ### [Bounce](/docs/sendgrid/glossary/bounces) *Email Deliverability*. A permanent rejection of messages sent from your IP address. ### [Bulk email service](/docs/sendgrid/glossary/bulk-email-service) *Marketing*. Software or service through which one sender can send one or many email messages to a large list of recipients. ### [Bulk mail folder](/docs/sendgrid/glossary/bulk-mail-folder) *Email Deliverability*. A location in a recipient's inbox into which the inbox provider routes email of questionable use or providence. [Back to top](#top) ## C ### [Campaigns](/docs/sendgrid/glossary/campaigns) *Marketing*. The act of sending customized email messages to a group of targeted recipient segments. ### [Canadian Anti-Spam Law of 2014](/docs/sendgrid/glossary/casl) *Regulation*. Canadian law that lists the guidelines, requirements, and penalties regarding the sending of commercial bulk email. ### [Canonical Name record (CNAME)](/docs/sendgrid/glossary/cname) *Internet standard*. A DNS record that maps one hostname in a domain to another hostname instead of an IP address. ### [Canonicalization](/docs/sendgrid/glossary/canonicalization) *Internet standard*. The standardization of email messages formatting that enables consistent hashed values for validating email messages. ### [Categories](/docs/sendgrid/glossary/categories) *Analytics*. One or more topical tags applied to an email message that aids in analyzing email campaign effectiveness. ### [Challenge-response spam filtering](/docs/sendgrid/glossary/challenge-response) *Internet Security*. A type of spam filter that replies with a challenge to the given sender. ### [Click-through rate (CTR)](/docs/sendgrid/glossary/ctr) *Analytics*. A metric of interest in content linked in an email message expressed as a percentage of recipients that click a link in your email message. ### [Clicks and unique clicks](/docs/sendgrid/glossary/clicks) *Analytics*. A record of each time a customer clicks any link in your Twilio SendGrid emails. ### [Complaint](/docs/sendgrid/glossary/complaint) *Reputation*. A record of an email recipient reporting an email message as spam. ### [Content delivery network](/docs/sendgrid/glossary/cdn) *Service Provider*. A global network of servers that stores and serves copies of website content to website visitors using the server geographically closest to each website visitor. ### [Controlling the Assault of Non-Solicited Pornography and Marketing Act of 2003 (CAN-SPAM)](/docs/sendgrid/glossary/can-spam) *Regulation*. US law that lists the guidelines, requirements, and penalties regarding the sending of commercial bulk email. ### [Custom fields](/docs/sendgrid/glossary/custom-fields) *Configuration*. Original contact attribute added to your email contacts. [Back to top](#top) ## D ### [Deferral](/docs/sendgrid/glossary/deferrals) *Email Deliverability*. A deferred status can occur when an ISP or mailbox provider can't to accept email from your IP address. ### [Deliverability](/docs/sendgrid/glossary/deliverability) *Email Deliverability*. The measure of how many emails sent that reach their intended recipients without issue. ### [Delivery](/docs/sendgrid/glossary/deliveries) *Email Deliverability*. A confirmation that an end recipient received the email that the sender had sent. ### [Demand-side platform (DSP)](/docs/sendgrid/glossary/demand-side-platform) *Advertising*. Software that helps advertisers or ad agencies buy digital ad inventory across publishers, supply-side platforms, and ad exchanges. ### [Direct response advertising](/docs/sendgrid/glossary/direct-response-advertising) *Advertising*. A advertising tactic where ad content encourages or prompts viewers of an ad to act or to engage with the ad directly. ### [Domain](/docs/sendgrid/glossary/domain) *Internet standard*. A human-readable branding for an individual or organization's presense on the internet. ### [Domain authentication](/docs/sendgrid/glossary/domain-authentication) *Internet Security*. Protocols and policies that specify IP addresses and domains as proof of identity of an individual or organization sending email messages. ### [Domain Name System (DNS)](/docs/sendgrid/glossary/dns) *Internet standard*. A hierarchical system of software and systems that translate a fully qualified domain name into an IP address. ### [Domain-based Message Authentication, Reporting and Conformance (DMARC)](/docs/sendgrid/glossary/dmarc) *Internet Security*, *Internet Standard*. A domain-based policy for determining the authenticity of the person or service sending email on behalf of a domain. ### [DomainKeys Identified Mail (DKIM)](/docs/sendgrid/glossary/dkim) *Internet standard*. An domain-based email authentication protocol that helps ISPs better identify legitimate email senders. ### [Drip campaign](/docs/sendgrid/glossary/drip-campaign) *Marketing*. An email marketing strategy that sends engagement email messages on a schedule. ### [Drops](/docs/sendgrid/glossary/drops) *Email Deliverability*. The removal of an email message to a specific recipient to protect the sender's reputation. [Back to top](#top) ## E ### [Email API integration](/docs/sendgrid/glossary/email-api-integration) *API*. The facilitation of automating key functions through the synchronization of a sender's email service provider with their platform and software tools. ### [Email Authentication](/docs/sendgrid/glossary/email-authentication) *Internet Security*. Technical standards to help ISPs and other receivers validate the identity of an email sender. ### [Email harvesting](/docs/sendgrid/glossary/email-harvesting) *Reputation*. The process of obtaining lists of valid email addresses other than affirmative consent of the recipients for the purpose of sending bulk email. ### [Email marketing](/docs/sendgrid/glossary/email-marketing) *Marketing*. The promotion of a commercial product or service conveyed in an email message. ### [Email reputation score](/docs/sendgrid/glossary/email-reputation-score) *Reputation*. The rating an internet service provider or inbox provider sets for email sent from your email server IP addresses. ### [Email service provider (ESP)](/docs/sendgrid/glossary/email-service-provider) *Service Provider*. A service organization that provides transactional and marketing email services. ### [Expandable Banner](/docs/sendgrid/glossary/expandable-banner) *Advertising*. A design of a digital advertisement that increases in size when a viewer clicks or hovers over the ad. ### [Expired](/docs/sendgrid/glossary/expired) *Email Deliverability*. The removal of recipient email address from a contact list when an SMTP server couldn't deliver an email message to the recipient within 72 hours. [Back to top](#top) ## F ### [Feedback loop (FBL)](/docs/sendgrid/glossary/feedback-loop) *Reputation*. A process where an service provider forwards emails reported as spam to a sender for removal. ### [Flighting](/docs/sendgrid/glossary/flighting-in-advertising) *Advertising*. The time in which an advertising campaign runs. ### [Frequency capping](/docs/sendgrid/glossary/frequency-capping) *Advertising*. The setting of a maximum number of times a specific viewer sees a specific ad. ### [Fully Qualified Domain Name (FQDN)](/docs/sendgrid/glossary/fqdn) *Internet standard*. A human-readable label that identifies a specific server on the internet. [Back to top](#top) ## G ### [General Data Protection Regulation of 2018 (GDPR)](/docs/sendgrid/glossary/gdpr) *Regulation*. European Union law that regulates the handling of personal data and outlines the rights individuals have regarding their data. [Back to top](#top) ## H ### [Header](/docs/sendgrid/glossary/header) *Internet standard*. Metadata that informs email recipients and servers of the routing, formatting, and security of an email message. [Back to top](#top) ## I ### [Internet Message Access Protocol (IMAP)](/docs/sendgrid/glossary/imap) *Internet standard*. The communication rules that systems follow to let you read and retrieve email messages from your inbox provider. ### [Invalid Email](/docs/sendgrid/glossary/invalid-email) *Email Deliverability*. The removal of recipient email address that doesn't conform to the [Internet Engineering Task Force (IETF)](https://www.ietf.org/) email address syntax standards from a contact list. ### [IP address](/docs/sendgrid/glossary/ip-address) *Internet standard*. A unique numerical address that identifies a virtual location on the internet. ### [IP warmup](/docs/sendgrid/glossary/ip-warmup) *Email Deliverability*. The establishment of a reputation as a legitimate email sender through the gradual and regular increase in the volume of email sent from one IP address. [Back to top](#top) ## L ### [Link branding](/docs/sendgrid/glossary/link-branding) *Marketing*. Change the domain for open and click tracking links to your domain. ### [Lists](/docs/sendgrid/glossary/lists) *Marketing*. Static collections of contacts to whom email messages can be sent. [Back to top](#top) ## M ### [Mail Exchanger record (MX)](/docs/sendgrid/glossary/mx-record) *Internet standard*. A DNS record that maps the hostname in a domain that accepts email for the domain. ### [Mail merge](/docs/sendgrid/glossary/mail-merge) *Marketing*. A process that generates customized email messages from a generic template and store of contact data. ### [Mail Transfer Agent (MTA)](/docs/sendgrid/glossary/mta) *Internet standard*. A system that transfers email messages from one computer to another using a client-server application architecture. ### [Mail User Agent (MUA)](/docs/sendgrid/glossary/mua) *Internet standard*. An app that you use to compose and send email messages. ### [Mailbox provider](/docs/sendgrid/glossary/mailbox-provider) *Marketing*. A service organization that provides transactional email services, marketing email services, or both. [Back to top](#top) ## N ### [Native advertising](/docs/sendgrid/glossary/native-advertising) *Advertising*. A type of advertising that resembles the content of the surrounding medium. [Back to top](#top) ## O ### [Open Rate](/docs/sendgrid/glossary/open-rate) *Analytics*. The frequency by which your customers open emails that you send. ### [Open relay](/docs/sendgrid/glossary/openrelay) *Internet Security*. An unsecured SMTP relay that routes email between domains. ### [Opens & Unique Opens](/docs/sendgrid/glossary/opens) *Analytics*. The record of each time a customer opens your Twilio SendGrid email messages. [Back to top](#top) ## P ### [Peer-initiated invitations campaign](/docs/sendgrid/glossary/peer-invitations) *Marketing*. A email marketing campaign designed to get customers to invite their friends and family. ### [Phishing](/docs/sendgrid/glossary/phishing) *Internet Security*. The act of masquerading as a trusted business to acquire personally identifiable information. ### [Pointer record (PTR)](/docs/sendgrid/glossary/ptr) *Internet standard*. A DNS record that maps an IP address to one hostname in a domain. ### [Preheader](/docs/sendgrid/glossary/preheader) *Marketing*. The short summary text that follows the subject line when you view an email in your inbox. ### [Programmatic Media Buying](/docs/sendgrid/glossary/programmatic-media-buying) *Advertising*. Process of buying paid media through sophisticated software that automates how the buying, placing, and optimizing of paid media. [Back to top](#top) ## R ### [Rate limiting](/docs/sendgrid/glossary/rate-limiting) *Email Deliverability*. See Throttling. ### [Reconfirmation email](/docs/sendgrid/glossary/reconfirmation) *Reputation*. An email message sent to existing recipients asking them to confirm that they still want your messages. ### [Request](/docs/sendgrid/glossary/request) *Analytics*. The record of an attempt to send an email through Twilio SendGrid. ### [Reseller email account](/docs/sendgrid/glossary/reseller-email-account) *Service Provider*. Email account created after a company entered into a partnership with Twilio. ### [Reserved fields](/docs/sendgrid/glossary/reserved-fields) *Configuration*. Predefined and protected attributes provided for email contacts. ### [Reserved substitution tags](/docs/sendgrid/glossary/system-fields) *Configuration*. Placeholder labels that get replaced with personalized content in an email campaign. ### [Reverse DNS](/docs/sendgrid/glossary/reverse-dns) *Internet Standard*. Method for systems to resolve an IP address from a domain name. [Back to top](#top) ## S ### [Scheduled Emails](/docs/sendgrid/glossary/scheduled-emails) *Marketing*. Configuring a system to send email messages starting at a given date and time. ### [Segmentation](/docs/sendgrid/glossary/segmentation) *Marketing*. The practice of channeling email traffic based on the intent and audience of email messages. ### [Segments](/docs/sendgrid/glossary/segments) *Marketing*. A dynamic collection of contacts grouped based on criteria you define. ### [Sender authentication](/docs/sendgrid/glossary/sender-authentication) *Internet Security*. The process that shows ISPs that you gave your mailbox provide permission to send emails on your behalf. ### [Sender ID](/docs/sendgrid/glossary/sender-id) *Internet Security*. A deprecated email authentication standard that checked that a domain authorized a given email address to send on its behalf. ### [Sender Policy Framework (SPF)](/docs/sendgrid/glossary/spf) *Internet Security*, *Internet Standard*. An email authentication standard that sets which servers can send email from their domain. ### [Senders](/docs/sendgrid/glossary/senders) Identity of the individual, position, or organization sending an email message. ### [Sends](/docs/sendgrid/glossary/sends) *Analytics*. A request for Twilio SendGrid to deliver email to your recipients. ### [Simple Mail Transfer Protocol (SMTP)](/docs/sendgrid/glossary/smtp) *Internet standard*. The communication rules that systems follow for the reliable and efficient transfer of email messages. ### [Single send](/docs/sendgrid/glossary/single-send) *Marketing*. A non-recurring email message that communicates non-automated, non-sequential content. ### [SMTP API](/docs/sendgrid/glossary/smtp-api) *API*. A progamming interface that provides customized email handling instructions on a per-email basis. ### [SMTP Provider](/docs/sendgrid/glossary/smtp-provider) *Service Provider*. A vendor that helps send large quantities of email messages to recipients. ### [SMTP relay](/docs/sendgrid/glossary/smtp-relay) *Internet standard*. A system that sends email between SMTP servers on different domains. ### [SMTP Server](/docs/sendgrid/glossary/smtp-server) *Internet standard*. An app or server that sends email and react to response codes from receiving servers. ### [SMTP service](/docs/sendgrid/glossary/smtp-service) *Email Deliverability*. Third-party managed service that delivers email messages to a large audience. ### [Spam](/docs/sendgrid/glossary/spam) *Reputation*. An email message sent to a recipient that they didn't request or want. ### [Spam Filter](/docs/sendgrid/glossary/spam-filter) *Email Deliverability*. Algorithms that identify and remediate unwanted email messages. ### [Spam report](/docs/sendgrid/glossary/spam-reports) *Reputation*. A feedback mechanism that identifies electronic messages as abusing the transmission medium and reports them to an authority for remediation. ### [Spam Traps](/docs/sendgrid/glossary/spam-traps) *Reputation*. Email addresses created without active owners to identify spammers and senders with poor data quality practices. ### [Spoofing](/docs/sendgrid/glossary/spoofing) *Internet Security*. A technique where a falsified sender email addresses attempts to trick recipients into opening an email message. ### [Subscriber list management](/docs/sendgrid/glossary/subscriber-list-management) *Marketing*. The validation that subscribers found in your contact lists remain active and engaged with your email marketing. ### [Suspicious Sender](/docs/sendgrid/glossary/suspicious-sender) *Reputation*. An email sender who sends email messages to recipients that never granted explicit permission to that sender. [Back to top](#top) ## T ### [Teammates](/docs/sendgrid/glossary/teammates) *Configuration*. Option that allows multiple physical users to share access to a single Twilio SendGrid account. ### [Throttling](/docs/sendgrid/glossary/throttling) *Email Deliverability*. A recipient inbox provider reduces throughput of email messages below the level at which sender mail server sent the email messages. ### [Time zone](/docs/sendgrid/glossary/timezone) *Internet standard*. Local time, based on your current geographic location on the earth. ### [Transactional email](/docs/sendgrid/glossary/transactional-email) *Marketing*. An email message sent in response to a user interaction with a web application. ### [Transactional Email Templates](/docs/sendgrid/glossary/transactional-email-templates) *Marketing*. A predesigned email layout, and sometimes content, that you can apply to transactional emails. ### [Transport Layer Security (TLS)](/docs/sendgrid/glossary/tls) *Internet Security*, *Internet Standard*. The set of rules that encrypts internet traffic between systems. ### [Triggered action](/docs/sendgrid/glossary/triggered-actions) *Marketing*. A task executed once a customer meets a pre-defined condition. ### [Triggered email](/docs/sendgrid/glossary/triggered-email) *Marketing*. An email message sent in response to specific events or actions. ### [Trusted sender](/docs/sendgrid/glossary/trusted-sender) *Reputation*. An email sender who only sends email messages to those recipients that granted explicit permission to that sender. ### [Twilio SendGrid message ID](/docs/sendgrid/glossary/message-id) *Marketing*. A unique identifier that Twilio SendGrid generates and assigns to an email message for event identification purposes. ### [Two- or multi-factor authentication (2FA or MFA)](/docs/sendgrid/glossary/two-factor-authentication) *Internet Security*. Use of two or more means of user identification to grant access to a system. [Back to top](#top) ## U ### [Undelivered Email](/docs/sendgrid/glossary/undelivered-email) *Email Deliverability*. A category of reasons why an email address wasn't sent to a recipient's inbox. ### [Unknown User](/docs/sendgrid/glossary/unknown-user) *Email Deliverability*. The removal of recipient email address that doesn't exist on the recipient email server from a contact list. ### [Unsubscribe](/docs/sendgrid/glossary/unsubscribes) *Email Deliverability*. A recipient's voluntary decision to remove themself from a sender's bulk email service. ### [Urchin Tracking Module (UTM) parameters](/docs/sendgrid/glossary/utm-parameters) *Analytics*. Five URL parameters added to links that marketers use to track online marketing campaigns. [Back to top](#top) ## W ### [Web API](/docs/sendgrid/glossary/web-api) *API*. A programming interface that allows web servers and web browsers to connect and enable account and data collection for services like email. ### [Webhook](/docs/sendgrid/glossary/webhook) *Analytics*. An event-driven communication that sends data between apps using custom HTTP POST request to a URL. [Back to top](#top) ## X ### [X-Message-ID](/docs/sendgrid/glossary/x-message-id) *Analytics*. An SMTP email header that Twilio SendGrid includes in email messages it sends as event webhook metadata. [Back to top](#top)