Email Service Provider

An email service provider (ESP) is software that sends and manages marketing and transactional emails at scale.

Definition & Examples

What is an Email Service Provider (ESP)?

An ESP is a platform for sending, managing, and measuring email at scale. It provides campaign tools, automation, templates, list management, and analytics for both marketing and transactional messages.

How it works

• Sending infrastructure: high‑reputation IPs and domains, queueing, retries.

• Message creation: editors, templates, personalization and dynamic content.

• Audience: list management, segmentation, and preference centers.

• Compliance: unsubscribe footers and legal details (editor footer, preference center.

• Analytics: opens, clicks, conversions; deliverability diagnostics (improving inbox placement).

Why it matters

• Reliability and scale: deliver millions of messages with high inbox rates.

• Efficiency: automation replaces manual one‑off sending.

• Insights: performance and deliverability data guide iteration.

Examples / Use cases

• Marketing campaigns, newsletters, and lifecycle automation.

• Transactional notifications like receipts, password resets, and alerts.

• Segment‑targeted sends based on behavior or lifecycle stage.

ESP vs SMTP relay

Common pitfalls

• Ignoring preference centers - leads to spam complaints. Fix: expose controls.

• Poor list hygiene - bounces and complaints harm reputation. Fix: clean lists.

• One shared API key everywhere - operational risk. Fix: scope and rotate keys.

Related terms

• Email campaign

• Email list

• Email deliverability

• Transactional emails

Key takeaways

• ESPs power at‑scale sending with compliance and analytics built in.

• Use preference centers and clear unsubscribe to reduce complaints.

• Monitor deliverability and iterate on content, cadence, and targeting.
  Have you ever wondered how all of these companies are able to send out boatloads of emails in a short amount of time and to customers with varying preferences and needs? Hint: they have some help.

They manage to do this with the help of an email service provider, or ESP.

But what is an ESP and why are they so important?

What is an Email Service Provider or ESP?

An email service provider (ESP) is a service that allows you to send email campaigns to a list of users/customers/subscribers.

Not only do they allow you to simply send email, they also provide the tools for designing these emails so that they consistently look good across all email clients, segmenting mailing lists based on customer demographics and data, scheduling the email sends for a later time, and tracking analytics.

Outside of the email sending, an ESP also allows you to grow and manage your email list much like a CRM does for managing contacts.

Why You Should Use an Email Service Provider

Email service providers allow your business to personalize email campaigns based on customer behaviors and preferences. This increases both engagement and overall conversion.

ELI5: Email service providers can actually result in more money for your business.

Additionally, ESPs allow businesses to track their email performance in real-time, allowing them to adapt and improve their strategies. Analytics worth tracking include open rates, click-through rates, and bounce rates among others.

Finally, ESPs help you follow email marketing laws and implement unsubscribe and preference management features.

Email Marketing Service Providers

Here are some ESPs that businesses often use:

• Loops

• Mailchimp

• Campaign Monitor

• MailerLite

• Brevo

• Klaviyo

• Aweber

Loops supports both marketing and transactional emails in one place; see docs for unsubscribe links, preference center, and deliverability guidance.

Key Takeaways

ESP stands for Email Service Provider.

An email service provider (ESP) is a service that allows you to send email campaigns to a list of users/customers/subscribers.

Using an email service provider is key for managing your email marketing activities.

Loops is an email service provider.