Deliverability: A term that refers to the best practices and authentication techniques of mass email communication that improve the likelihood that opt-in email messages are successfully delivered to end recipients instead of being erroneously blocked by ISPs and spam filters.

Discussion group: An email list community where members can obtain and share information. Every member can write to the list, and in doing so, everyone subscribed to the list will receive a copy of the message.

Distribution list: A single email address that resends to many others, allowing a discussion to continue easily among a quasi-stable group of participants. Also called emailing lists or listservs (from LIST SERVers).

DomainKeys/DKIM: DomainKeys/DomainKeys Identified Mail are cryptographic authentication solutions that add signatures to email messages, allowing recipient sites to verify that the message was sent by an authorized sender and was not altered in transit.

Domain Throttling: A technique that allows you to limit the number of email messages sent to a domain within a certain time frame. It is used to comply with ISPs and to avoid tripping spam filters. Many ISPs have their own policies and preferred limits.

Double opt-in: The recommended procedure for subscribing email recipients to an email list or newsletter. Once a person requests to subscribe to a list, a confirmation email message is automatically sent to the supplied email address asking the person to verify that they have in fact requested to be included in future mailings.