---
title: "Email Service Provider (ESP)"
description: "An Email Service Provider (ESP) is an organisation that offers email hosting and management services, allowing users to send, receive, and manage emails."
url: "https://mailmum.io/glossary/email-service-provider-esp/"
---

# Email Service Provider (ESP)

An Email Service Provider (ESP) is a third-party company that offers email
hosting and management services, allowing users to send, receive, and manage
emails. ESPs typically provide services by managing email servers and other
related systems.

The term is used loosely, and its meaning depends on who you ask — see
[ESP, mailbox provider or MTA?](https://mailmum.io/glossary/email-service-provider-esp/#esp-mailbox-provider-or-mta) below, because
the distinction matters as soon as you start diagnosing a delivery problem.

## Who can be an email service provider?

An Email Service Provider (ESP) can be any person, company or organization that
provides email hosting and management services. This can include:

* Single person running an email server for him/her or a group of persons like
  family.
* An organisation or company running their own email system.
* Web hosting companies that offer email hosting as part of their hosting plans.
* Email marketing companies that specialize in email marketing campaigns and
  provide features such as email creation, list management, and campaign
  tracking.
* [Internet service providers (ISPs)](https://mailmum.io/glossary/internet-service-provider-isp/)
  that provide email accounts to their customers.
* Cloud-based email providers that offer email services through a web-based
  interface or application.
* Enterprise-level email providers that offer advanced email management and
  security features for large organizations.

In general, any person, company or organization that has the infrastructure and
expertise to provide reliable and secure email services can be an Email Service
Provider (ESP).

## ESP, mailbox provider or MTA?

In the deliverability world, "ESP" is often used in a narrower sense than the
broad definition above, and three terms get mixed up regularly:

* **ESP (sending platform)** — a service you send *through*. It provides
  an API or SMTP endpoint, manages the sending IP addresses and their
  reputation, and handles bounces, unsubscribes and campaign reporting.
  Examples: Mailchimp, SendGrid, Postmark, Brevo, Amazon SES.
* **Mailbox provider** — a service that hosts the recipient's mailbox and
  decides whether your message reaches the inbox, the spam folder, or nothing
  at all. Examples: Gmail, Outlook.com, GMX, Web.de, Yahoo. These are the
  systems whose filters you are actually up against.
* **[MTA](https://mailmum.io/glossary/mail-transfer-agent-mta/)** — the software doing the
  actual SMTP transfer, such as Postfix or Exim. An ESP runs MTAs; so does a
  mailbox provider; so does a company running its own mail server.

The practical reason to keep them apart: if mail is not arriving, "the ESP" and
"the mailbox provider" are two different parties with two different sets of
logs, and the fix lives with one of them. An ESP can tell you the message was
accepted; only the mailbox provider decides where it landed.

## What does an ESP do for deliverability?

A sending platform typically takes on work that is otherwise yours to do:

* Maintaining a pool of sending IP addresses with established reputation, and
  keeping them off [IP blacklists](https://mailmum.io/glossary/ip-blacklisting/).
* Setting correct [reverse DNS](https://mailmum.io/glossary/reverse-dns-rdns/) for those IP
  addresses.
* Publishing and managing SPF, DKIM and DMARC records, or giving you the
  records to publish on your own domain.
* Processing [bounce messages](https://mailmum.io/glossary/bounce-message/) and suppressing
  addresses that hard bounce, so you do not keep sending to dead mailboxes.
* Handling unsubscribe headers and complaint feedback loops from mailbox
  providers.

None of this removes your own responsibility for what you send. Reputation
follows the sending domain as well as the IP address, and a shared IP pool
means your results are partly affected by the other customers on it.