One type of email service provider (ESP) is an organization which provides email servers to send, receive, and store email for other organizations and/or end users. Such an ESP may provide the service to the general public for personal email (e.g. Yahoo Mail, Hotmail, Gmail, AOL Mail, Pobox and many others) or it may provide the service only to its members (e.g. subscribers, employees of a business, college alumni associations, professional organizations, etc). An ESP may be a division of a much larger organization whose primary function is not email (e.g. Google owns Gmail) or it may be an email specialist (e.g. Pobox). An Internet Service Provider (ISP) which provides Internet access to end users is almost always an ESP too. An ESP's services are typically paid for by subscription, as part of membership, or through advertising. Users may access their email via webmail, POP3 or IMAP protocols depending on the policies of the ESP. This type of ESP does not generally condone the sending of bulk email through their servers, plus they frequently employ filters to prevent spam from entering their customers' in-boxes.
The other type of email service provider, a commercial ESP, is a company which offers email marketing or bulk email services. Neither of these terms is intended to be synonymous with spam or the sending of unwanted or unsolicited bulk email of a marketing or otherwise offensive nature.[1]
A commercial ESP may provide tracking information showing the status of email sent to each member of an address list. ESPs also often provide the ability to segment an address list into interest groups or categories, allowing the user to send targeted information to people who they believe will value the correspondence.
A commercial ESP will provide a service which may include the following features:
The level of service provided can be according to the above basic features, or the number of subscribers uploaded, or the frequency of use – or any combination of the above criteria.
ESPs of both types typically have terms and conditions (such as an Acceptable Use Policy) to prevent abuse by users in order to ensure that no spam is sent through their systems. This is intended to result in the best possible delivery rates, with no messages blocked as spam. Some ESPs work with Internet Service Providers (ISPs) to ensure compliance with legalislation and best practices, through organizations such as the Messaging Anti-Abuse Working Group.