Glossary part I: A through D

A/B/C split testing: A test in which a list is split into two or three parts and sent different subject lines so that the sender can see which performs better.

Alt text: Text that appears in place of an image before it’s downloaded in the inbox. (This is the "description” when uploading an image in the application.)

API (application programming interface): An interface that allows communication between two different applications via software.

Bounce: An email message that doesn’t get delivered to a recipient's inbox. There are two types of bounces:

  1. Soft bounce: An email sent to an active email address, but then is turned away before being delivered. Often, the problem is temporary -- the server is down or the recipient's mailbox is full. The email might be held at the recipient's server to be delivered later, or the sender's email program may attempt to deliver it again.
  2. Hard bounce: An email sent to an invalid, closed or nonexistent email account (no connection is made to the recipient’s server).

Best practices: Guidelines for email marketers and designers to follow that will ensure the most effective results in an inbox.

CAN-SPAM: The U.S. law regulating commercial email -- requiring a truthful subject and from address, an opt-out link and a physical mailing address.

Deliverability: An ESP's ability to deliver emails to various recipient servers.