Back to main menu



Lost in all the technical jargon? Find definitions for common email and technical terms and learn more with our related resources.


Throttling is the practice of restricting the bandwidth of brands to carry out operations. In emails, throttling occurs when internet service providers (ISPs) limit the number of emails a brand can send for a specified period of time. During this period, a brand receives notices of temporary delivery failures, or soft bounces. This usually happens when ISPs detect that the brand’s IP address has suddenly ramped up its sending volume, which looks spammy. ISPs then throttle the domain while figuring out whether or not the domain is a legitimate sender.

Tracking pixel

A tracking pixel is a 1:1 pixel graphic generated by a line of code in an email. It tracks user behaviors and delivers personalized marketing to users as they browse the internet. Brands embed tracking pixels in either email headers or footers. Unlike cookies, which are highly noticeable and can be disabled, tracking pixels are virtually invisible to email subscribers.

Transactional email

A transactional email is automatically sent when triggered by user actions, like purchases or password reset requests. Transactional emails are also sent when a brand needs to share information with a subscriber, like order confirmations or payment received notifications. These are typically templatized and personalized since they’re only relevant to a particular user’s action. Because transactional emails are automated, most brands collaborate with an email service provider (ESP) like Mailgun, which sends the emails via an Application Programming Interface (API).

Transport Layer Security (TLS)

Transport Layer Security (TLS) is an encryption standard that protects emails and sensitive information during the sending and receiving process. It also authenticates the sender and verifies email content and data to ensure the data has not been tampered with.

Triggered emails

Triggered emails, also known as behavioral emails or transactional emails, are email messages sent automatically, based on user actions or specific events. They rely on customer data and behaviors. For instance, if a user purchases a product from a webshop, the brand will schedule an email automation trigger to send an order confirmation message.