Affirmative Consent
The U.S. Senate Commerce Committee Report for the CAN-SPAM Act indicates that "affirmative consent" requires some active choice or selection by the recipient. A passive, such as not un-checking a pre-checked box or other default Web form, is not sufficient. Source: Commerce Committe Report, CAN-SPAM Act of 2003

Bounce
A message that doesn't get delivered promptly is said to have bounced. Emails can bounce for more than 30 reasons, e.g., the Email address is incorrect or has been closed; the recipient's mailbox is full; the mail server is down; or the system detects Spam or offensive content
(See hard bounce and soft bounce).

Bounce handling
The process of dealing with the Email that has bounced. Bounce handling is important for list maintenance, list integrity and delivery. Given the lack of consistency in bounce messaging formats, it's an inexact science at best.

Calls to Action
Words that offer the opportunity and encourage the prospect to take action. For example, "Click here to see a product tour" or "Add this product to your wish list."

CAN-SPAM
Popular name for the U.S. law regulating commercial Email (Full name: Controlling the Assault of Non-Solicited Pornography and Marketing Act of 2003

Click-through
When a recipient clicks on a link.

Confirmed opt-in
Also referred to as Double Opt- in, this is a two-step process to allow a user to opt-in to (join) your list. They must initially sign up, and then respond to a follow up Email to opt-in to your mailing list.

Open Rate
The number of Emails opened, divided by the total number of Emails sent, multiplied by 100.

Opt-out
The action a person takes when they choose not to receive communications. It requires mechanisms by which people can ask to be removed reliably from an Email list.

Privacy
The quality, or condition of being free from unsanctioned intrusion. Privacy in the Email marketing world implies that a recipient's Email address is not, nor will it be shared, and they will not receive Email they did not otherwise request as a consequence.

Spam
Email sent without the recipient's permission. Also known as UCE, or Unsolicited Commercial Email.

Tracking
Collecting, arranging and evaluating the statistics through which one can measure the effectiveness of an Email or an Email campaign.

Unique Click
A unique click is a single click by a single user. When unique clicks are measured, it is an aggregate number of how many times that URL was clicked by individual users (not the complete total of all users,
all clicks).

Block
An action by an Internet Service Provider (ISP) to not forward your Email messages to the recipient. This is a distinct and separate activity from a bounce.

Bounce message
Message sent back to an Email sender reporting the message could not be delivered and why. Note: Not all bounced Emails result in messages being sent back to the sender. Not all bounce messages are clear or accurate about the reason the Email was bounced.

Bounce rate
(Also return rate) The number of hard/soft bounces divided by the number of Emails sent. This is an inexact number because some systems do not report back to the sender clearly or accurately.

Campaign
A coordinated set of individual Email marketing messages delivered at intervals, and with an overall objective in mind. A campaign allows each new message to build on previous ones.

Catch-all
An Email server function that forwards all questionable Email to a single mailbox. The catch-all should be monitored regularly to find misdirected questions, "unsubscribes" or other valid Email.

Click-through rate
To determine the click-through rate, divide the number of responses by the number of Emails opened (multiple this number by 100 to express the result as a percentage).

Double opt-in
Also referred to as Confirmed opt-in, is a two-step process to allow a user to opt in to your list. They must initially sign up, and then respond to a follow up email to opt in twice to your mailing list.

Opt-in
Opt-In is the action a person takes when he or she actively agrees, by email or other means, to receive communications. (Also see Double Opt in)

Personalization
The practice of creating an Email that the recipient feels is more personal. Personalization can include a number of things, such as mail merging a name into the subject line, referring to previous purchases, or more dynamic content based on demographic fields.

Soft Bounce
The failed delivery of an Email due to a temporary reason, such as a full mailbox or unavailable server.

Subject Line
The title of the Email communication. This is the first element of the communication recipients will see when they access their email. It should grab attention, be accurately descriptive of the content of the Email and be credible.

UCE
Unsolicited Commercial Email (also referred to as Spam). Commercial email sent without the recipient's express permission.