---
title: "Internet Service Provider (ISP)"
description: "An Internet Service Provider (ISP) is a company that provides internet access to customers. It does this by providing a connection to the internet via a network of servers, which allows users to access the web, send emails, and use other internet services."
url: "https://mailmum.io/glossary/internet-service-provider-isp/"
---

# Internet Service Provider (ISP)

An Internet Service Provider (ISP) is a company that provides internet access to
customers. It does this by providing a connection to the internet via a network
of servers, which allows users to access the web, send emails, and use other
internet services. ISPs can be large, national companies or smaller, local
providers.

## Do ISPs provide email services?

Some Internet Service Providers (ISPs) do offer email services to their
customers as part of their internet package. This means that when you sign up
for internet service with a particular ISP, you may also be given a unique email
address that you can use to send and receive emails. However, not all ISPs offer
email services, and you may need to use a separate email provider, to create and
manage your email accounts.

## Do ISPs use IP Blacklisting in their email services?

It is possible for Internet Service Providers (ISPs) to use [IP
blacklisting](https://mailmum.io/glossary/ip-blacklisting/) to block certain incoming emails from
reaching their customers' inboxes. It is a security measure used to block
emails from known spam sources, or from sources that have been identified as
potentially harmful. When an IP address is added to a blacklist, emails sent
from that address may be automatically blocked or flagged as spam before they
reach the recipient's inbox.

Not all ISPs do this, and the techniques vary from one provider to another.
Content filtering, reputation-based filtering, greylisting and rate limiting
are all used alongside — or instead of — blacklists.

## Do ISPs use IP Whitelisting in their email services?

Many ISPs maintain the inverse of a blacklist: a list of trusted IP addresses
whose mail is allowed to skip some or all of the usual checks. This is commonly
called IP whitelisting or, on the DNS side, a DNSWL (DNS-based whitelist).

In practice a whitelisted source is treated in one of two ways:

* **Bypass** — the connection skips blacklist lookups and some spam
  checks entirely. This is normally reserved for the ISP's own infrastructure
  and a small number of known partners.
* **Negative scoring** — the message is still filtered, but the listing
  contributes a score in the sender's favour, making a spam verdict less
  likely. This is the more common and more cautious approach.

Mail from everything else goes through the normal path, including blacklist
lookups and content filtering.

Getting onto an ISP's whitelist is not something you can generally request as a
one-off favour. It usually follows from a consistent sending history: correct
[reverse DNS](https://mailmum.io/glossary/reverse-dns-rdns/), authenticated mail, low complaint
rates, and a working abuse contact. Some larger
providers run formal programmes with their own application process and
requirements.