Cc: Carbon Copy -  When you send an e-mail message, you typically type the recipient's address in the "To:" field. If you want to send the message to one or more other recipients, you can use the "Cc:" field to add additional addresses. This will send the e-mail to the address in the "To:" field and to each address listed in the "Cc:" field as well.

Challenge-Response: An authentication method that requires a human to respond to an email challenge message before the original email that triggered the challenge is delivered to the recipient. This method is sometimes used to cut down on spam since it requires an action by a human sender.

Click-through tracking: The process of tracking how many recipients clicked on a particular link in an email message. This is commonly done to measure the success of email marketing campaigns.

Click-through rate: In an email marketing campaign, the percentage of recipients who clicked on a particular link within the email message.

Conditional blocks: A text fragment that is pasted into an email message only if certain conditions are met (for instance the recipient lives in a certain area). Conditional blocks allow email marketers to create more personalized mailings.

Conversion rate: A measure of success for an email marketing campaign (for instance the number of recipients who completed a purchase). With email marketing, conversion rates are relatively easy to calculate because of the technology's measurable nature.