Features, Nuts & Bolts

How Email Service Providers Work in 2019

With billions of potential customers relying on email, email service providers are essential marketing resources.

Marshall Lemon
September 24 2019

When it comes to advertising campaigns in the modern world, marketers often focus on the benefits created by smartphone technologies. While these developments are certainly important, they often lead us to overlook less flashy opportunities — including the humble email campaign.

By 2022, a projected 4.3 billion users will have an email account and a total of 333 billion emails will be delivered each day. That’s an impressive reach for marketers who see an ROI of up to $32 for every dollar invested in email marketing. To maximize the value of email, marketers segment and target large audience networks with an email service provider (ESP).

As part of PostFunnel’s Nuts and Bolts series, we’ll delve into the world of modern Martech to shed some light on tools and best practices being used by you – our fellow marketers – in your day-to-day strategies. Every month, our experts will sink their teeth into another aspect of this fascinating field, hopefully inspiring you to elevate your business through smart marketing.

What is an email service provider (ESP)?

An email service provider is a business solution that offers email marketing and/or bulk email delivery. Marketers use ESPs to manage every aspect of an email marketing campaign, from plan and design, through distribution to reporting.

Along with managing email campaigns, some ESPs also support advanced features such as dynamic email tools. These features, popularized by solutions like Dynamic Email, integrate personalized elements that automatically change to reflect the user. For example, dynamic content can be used to display the user’s name in a greeting message or offer a targeted promotion. When integrated with emails and online newsletters, dynamic content makes each communication more engaging and immersive when compared to traditional static emails.

What email services are there?

Of course, marketers turn to ESPs for more than just their ability to send emails. Many providers will offer all of the following services, or some variation thereof:

  • Email templates: ESP templates allow marketers to generate emails quickly without designing the layout themselves. Templates can include images and pre-optimized for mobile devices.
  • Subscriber lists: Each provider will need subscriber lists to know which accounts will be receiving emails. These can be enhanced optionally with custom fields for targeting purposes.
  • Campaign tracking: A consolidated dashboard allows marketers to monitor all aspects of a launched campaign. This usually includes tracking of essential KPI — metrics like open rates, clicks, and unsubscribes — while offering the option to output reports.
  • Deliverability services: ESPs can offer deliverability services, increasing the likelihood of emails reaching a recipient’s inbox. These features are described in more detail in a later entry.
  • Automated delivery: Being able to send mass emails is great, but an optimized campaign should be able to target specific recipients during an ideal time of day. Automation functions allow marketers to automate email delivery with ease.

While ESPs share some functionality with customer relationship management solutions (CRMs), they often differ in their intended purposes. Where ESPs deal exclusively with email campaigns, CRMs often lack advanced features to focus more broadly on customer relationships. Some platforms do allow customers to integrate each solution where the option exists.

What is CAN-SPAM?

CAN-SPAM is an act passed into United States law in 2003. It stands for Controlling the Assault of Non-Solicited Pornography And Marketing and provides regulations for sending commercial email messages and managing associated email lists.

In short, CAN-SPAM addresses the following email content and messaging guidelines:

  • Subscriptions: Users must be able to unsubscribe from an email list at their convenience. Businesses cannot charge a fee for users to unsubscribe, request personal information for confirmation, or otherwise create additional steps or barriers outside of including an unsubscribe link within the email. Requests to unsubscribe must be fulfilled within ten business days.
  • Content: All commercial emails must include a valid physical address and a subject line that accurately describes its content.
  • Sending behavior: Emails must include clear “From” and “Reply to” addresses along with other signifiers that represent the commercial entity’s identity.
  • Email address management: Commercial entities cannot sell or transfer email addresses from one list to another.

Businesses that fail to comply with CAN-SPAM face severe consequences, up to and including $16,000 fines per email. Since modern campaigns can send identical emails to thousands of addresses, marketers must follow CAN-SPAM to the letter. The full-text is available from the FTC’s website.

What factors affect email deliverability?

For all the potential of email marketing, the benefits won’t materialize if users cannot read them. That makes email deliverability one of the most important elements a marketer can address — and also the most challenging. Various factors can influence whether an email will be received, send to a junk folder, or stopped from arriving entirely.

IP address

An IP address does more than act as a unique identifier — it also reflects the owner’s reputation with internet service providers. An IP address with a low reputation that tries to send mass emails might find its communications blocked to prevent fraud.


Web domains can have reputations that are independent of IP addresses. Internet service providers may prevent email transmissions from domains that are flagged.

Recipient behavior

Some email platforms and internet service providers use delivery algorithms to adapt to user behavior in ways that impact deliverability. For example, if a user frequently deletes emails without opening them, algorithms would start moving similar emails into a junk folder.

Email content and subject lines

Email content — either from the body or subject line — can trigger spam filters if they rely on certain commonly used phrases or links associated with spam and fraud emails.

What do ESPs do to improve deliverability?

ESPs can mitigate or fully address many of the factors that restrict email deliverability:

Increasing IP reputation

ESPs can deliver emails from a dedicated IP, ensuring that the address reputation is largely under their control. Alternatively, ESPs may offer shared IP addresses that allow smaller brands to benefit from pooling their email with established brands.

Implementing IP warmups

ESPs can gradually increase the volume of emails sent to certain addresses to avoid triggering spam algorithms.

Offering email consultancy

ESPs can offer email design and consultancy services to prevent email from being flagged as spam. This is often achieved by making content and subject line recommendations.

Increasing engagement

ESPs can apply engagement strategies that encourage users to open emails. Along with the consultancy options described above, this might include adjusting send frequency or deleting unengaged subscribers.

What should the marketing team do to improve deliverability?

Not all deliverability issues have to be resolved using an ESP. Marketing teams can address them directly using a variety of simple strategies, some of which are also supported by providers:

Comply with email delivery regulations

The easiest way to improve your deliverability is to ensure every email fully complies with CAN-SPAM and other regulations. Since marketing emails can be delivered internationally, don’t forget to tailor communications for each region you are conducting business in.

Periodically review your mailing lists

When users neglect to open emails, that can significantly reduce your engagement rates over time. One valuable solution is to conduct periodic refreshing of subscriber lists, removing clients who have not engaged within a certain interval. Instead, marketers can target these users for re-engagement campaigns that provide reasons to reconnect with the brand.

Use trusted links

While generic URL shortlists are useful on social media, some providers will blacklist them and harm deliverability. Take the time to verify each link connects directly to a trusted source to resolve this issue.

Avoid spam filter phrases

It’s worth researching some common phrases that will automatically send your emails to a spam filter and removing it from all communications. Doing so prevents algorithms from targeting your emails as spam, and may even encourage users to open engaging emails.

Here are a few common phrases to avoid:

  • Win
  • Don’t hesitate
  • 50% off
  • Join millions of Americans
  • Exclusive deal

Distinguish between transactional and promotional emails

Not all emails a brand sends to customers will be promotional. Some are transactional, meaning they occur in reaction to activity from the end-user. Examples range from resetting passwords to completing an online purchase.

By creating a clear distinction between each communication type, each email is much more likely to arrive at its intended inbox. Consider the language and branding elements behind each purpose when crafting your email templates.

While ESPs can greatly assist marketers in managing email campaigns, they are not without limitations. Many email hosts have restrictions on emails sent per day, emails sent per hour, and attachment file sizes. That being said, ESPs are essential tools for optimizing your marketing communications. They ensure each email reaches the intended inbox instead of being blocked by a spam filter. That makes ESPs an important resource that marketers shouldn’t overlook in 2019.

Marshall Lemon

Marshall Lemon is a writer, editor, librarian, and game designer. As the Content Marketing Manager at Fluid PR Group, he helps businesses craft engaging stories within the context of well-researched industry data. He lives in London, Ontario with his wife and two adorable puppers.

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