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If you send anywhere between 0-5 million emails per month, you are grappling with a problem of plenty when picking a mass email service.

Because of stiff competition in the inbox (126 emails per day for an average American) you  need to deploy strategies that were previously feasible only for deep pocketed enterprises. 

Fortunately, bulk email service software providers are upgrading themselves. From simple features, many tools are offering advanced features like: 

  • Predictive personalization
  • Dynamic segmentation.
  • Send time optimization 

Deployed imaginatively, these features will help you integrate email more tightly with other customer-facing channels and improve your brand.

The rub, though, lies in picking and choosing the right blend of features from a list of at least 400 ESPs.

A wrong tool can mess up your brand’s reputation, waste valuable time, and impose exorbitant opportunity costs.

This advanced buying guide seeks to solve these problems, which a business or an individual usually face while picking a Mass Email Service

Why check out this guide?

This guide is about helping you select a mass email marketing tool that will meet your needs in 2020 and beyond by covering less than obvious features that you should look out for.

We are considering full fledged ESPs here, instead of SMTP vendors.

In this guide, we are not going to be talking about well known email marketing tactics or features.

We are also not going to be recommending any names; just give you enough information to make a right decision.

Table of Contents

The Segmentation and Personalization Duality
The Deliverability Dilemma.
The Content Cliffhanger
The Analytics Arbitrage.
The API/Integration Combination
The Pricing Descision.
The Security and Compliance logjam.

1. The Segmentation and Personalization Duality

If you really want to nail your email game, you can’t afford to gloss over segmentation and personalization (S&P).

However, we are not talking of segmentation in terms of manually grouping your list into groups based on some attribute, or personalization in terms of addressing your user by FNAME.

Nope, we are talking about deep personalization, like NPR’s customized year-end review email.


This is what we call S&P2.0, and there’s enough data to prove it is a game-changer.

Here the features you should look out for if you want to really implement S&P2.0 in your email stack.

i) Website/in-app activity-based segmentation

That NPR email is a great example of in-app activity-based segmentation.

Your email tool of choice should let you set a few rules that highlight different user segments (traffic source, time on a particular page, minutes spent on a particular video, incomplete checkout) and:

  • Auto-populate and auto-curate these segments.
  • Send out relevant emails automatically(welcome email, cart abandonment email, product recommendation email etc)
  • Display not just email metrics like open/click-through rates, but product engagement or revenue metrics.
Recommended product email

Post purchase, personalized recommendation email

ii) RFM based Dynamic Segmentation

RFM stands for the Recency-Frequency-Monetary model, which takes into account three different aspects of a user’s past behavior to predict future actions.

With RFM analysis, you divide customers into different segments based on how recently, how frequently, and how much they transact on your store.

Here's how some of these segments might look like (click here for more on RFM analysis):

RFM Customer Segmentation

Customer Segment Customer Activity Email Tip
Champions Buys most often, and are very responsive to promotions Email them with upsells, ask for reviews
Potential Loyal Customers Have bought more than once, and have bought recently Email them with with membership or loyalty offers, and send product recommendations
Recent Customers Bought most recently, but infrequently Email them with support resources like guides etc that can get them value with their purchase
About to churn Customers with below average recency, frequency and monetary values Email with popular products, offer discounts, rebuilt your connection
Asleep customers Haven't bought anything for a very long time Email them with special product offers based on last purchase, highlight changes and re-establish brand's value proposition

If you have an ecommerce store, look for RFM based dynamic segmentation in your mass email tool to improve user experience and conversion rates.

iii) Integrated AI capabilities

AI plays a massive role in enhancing S&P 2.0 capabilities of modern email tools. Some examples include:

  • Predictive personalization: Thanks to rich user data, Natural Language Generation tools like Phrasee have outperformed humans by 98% when it comes to writing email copy. These tools are life-savers in use cases where you might need to write emails for 100s of customer segments.
  • Automated workflows: AI to automatically set up and fire email sequences based on different triggers and user behavior, saving user effort and time involved in creating manual workflows.
  • Testing at scale: Running A/B and multivariate tests and picking winners is also going to be one of the many tasks outsourced to AI, especially when you have hundreds of segments. 

For the email marketer of 2020, AI is not going to make your job redundant. It's going to be like any other tool, making your life simpler and lessening the drudgery of your day.

Go to Table of Contents

2. The Deliverability Dilemma

Sending perfectly crafted emails is one half of winning the battle for the inbox.

The other half is about ensuring that email actually gets seen by the recipient.

Email deliverability is still a bit of a dark art, and there are a number of  factors and variables that can influence your email deliverability.

Some of them are not in your control, but you can improve your chances by optimizing for the factors which you can influence.

Glossary of Little Known but Important Factors
Influencing Email Deliverability

Inbox Placement Rate
This metric measures the percentage of send emails delivered to subscriber inboxes. Low inbox placement rates indicate that your emails might be landing in spam folders or have bounced back because of incorrect email.

Seed list
This is a list of test email addresses used by email service providers to determine inbox placement rate, as well as understand spam placement and bounce rates.

This is an email authentication technique that uses a digital signature in the email header to help the receiver check whether an email was actually sent from the sending domain. 

The SPF is another email authentication technique that specifies which email servers are authorized to send email for your domain, and prevents spammers from sending messages on your behalf.

It's a reporting code for SPF and DKIM authentication. It helps the recipient server identify what steps to take with the email in case of authentication failure

BIMI is a hot new protocol that lets authenticated senders display their brand logo in the inbox.

Here are some of the ways you can stack the deck in your favor, and improve your email deliverability.

i) Email reputation

Your email reputation is built on three distinct factors:

  • Domain reputation based on factors like DMARC/BIMI implementation, Google postmaster score, presence (or absence) on spam blacklists etc
  • IP reputation based on factors like spam complaint rate, Returnpath senderscore, and inbox placement rate.
  • Content reputation based on factors like structure of email content, spam trigger words in the subject line, and metadata like alt-text in the email body.

We have previously written about how to measure and improve your email reputation, which you should routinely check for.

Your 2020 mass email service should make it easy for you to check against these metrics (through integrations).

It should also prompt you to adopt email authentication enhancers like DKIM, SPF, and DMARC, and possibly be compliant with BIMI.

This mindmap highlights the different factors influencing email reputation.

ii) AI and ML- Powered Email Deliverability

One of the most appropriate use cases for deploying AI and ML models in email is in deliverability optimization.

By analyzing both real-time and historical data your email tool should:

  • Adjust delivery rates (or pause it) if email delivery rate plummets, and suggest troubleshooting tips. 
  • Automatically warm up a new IP address by adjusting email delivery volume based on delivery rates, bounce rates, open rates etc.
  • Predict and actively boot out bad actors who might use the email service for malicious purposes.

iii) List Hygiene and User Sunsetting

Users churn out all the time, but many brands unintentionally hoard emails of past users or customers and keep on sending them irrelevant emails. 

This can adversely affect your email deliverability and ruin your domain and IP reputation.

Your mass email service tool should let you implement an active sunsetting policy by automatically scrubbing inactive email address at regular intervals.

user sunsetting on mass email performanceiv) Send Time Optimization

Send time optimization can radically improve your email deliverability and engagement metrics by delivering email when the user is most likely to see it.

Your mass email service will analyze the historical open times of each subscriber on your list, and deliver the email at the optimum time, regardless of when you hit send.

send time optimization for mass email

Send time optimization using Smartech, a Pepipost partner

Go to Table of Contents

3. The Content Cliffhanger

Mass email services email content

Ever since email marketing was invented, the inbox served as a pitstop to the ultimate destination. 

Whether you wanted to buy a product or read something, you ultimately had to click away from the email, and land somewhere else.

But this is changing in 2020.

Thanks to interactive content and AMP, email can be now the destination, allowing users to interact with it much like they would do a web page or an app.

Video is also a promising frontier- one stat indicated that click-through rates of emails with video increased by 96%!!

And there’s voice- with smart speakers like Google Alexa and Amazon Echo sold in millions, your emails have to be compatible with voice as well- see this video for a demonstration of how Alexa reads emails.

So, here’s what your email tool should be able to accomplish in terms of enabling content so that you don't fall behind in 2020.

i) Mobile optimization

Email consumption statistics by device type, as this graph shows, highlights the importance of optimizing your email campaigns for mobile.

Email on mobile vs desktopMarketers are responding to this change, and 73% of companies are sending mobile optimized emails. 

While there are multiple best practices in optimized emails for mobile, your email service provider should offer up mobile-optimized templates that make the creation of these emails simple and painless.

ii) Interactive Emails with AMP

Thanks to the implementation of AMP in emails and major ISPs like Gmail supporting this standard, emails are no longer boring. 

With timers, digital scratch cards, animated images, image carousels etc, interactive emails are driving 3x more engagement compared to static emails.

AMP emails

Example of an AMP email

Your email service provider pick should support AMP in emails so that you can get ahead of the crowd and reap the benefits of high engagement and provide a better user experience right inside the inbox.

iii) AI- Powered Subject Line Optimization

When your email list is made up of hundreds of user segments, and when you might be running A/B tests on each of those segments, it is humanly impossible to create the content for those hundreds of variations.

Enter Subject Line Optimization and dynamic content generation, powered by AI and ML models.

Working off training data, the machine learning models can automatically create subject lines and email content for as many emails as you need and set everything up so that they are ready to be sent and tested.

You can select the content based on:

  • The estimated open rate for a subject line
  • Comparison with historic subject line performance data
  • Inbox placement rate
  • Sentiment analysis,

Without these features, your mass email tool will not make you an efficient marketer.

AI powered subject line optimization

Subject line optimization powered by Smartech, a Pepipost partner

Go to Table of Contents

4. The Analytics Arbitrage

Your email analytics data often conceals more than it reveals. Analytics in mass email services

It’s easy to believe that data on open/click rates, unsubscribes, bounces, etc is enough to give you actionable insights into your email marketing performance.

None of these metrics will give you insights like:

  • Actual engagement metrics with a particular email in terms of time spent on it
  • Post click behavior of a particular user across multiple campaigns

Collecting and analyzing these metrics will give you a much better idea of the impact of your email marketing.

Your mass email tool of choice should present other types of data as well, like:

i) Time to Inbox

Depending on different factors like  IP throttling, ISP rules or network congestion, your mass email might take anywhere from 1 minute-5 days to be delivered to the recipient’s inbox.

In case you are sending time-sensitive emails like password resets or OTPs, it’s important that your mass email tool provides time to inbox data so that you can ensure timely delivery of email. 

(For Pepipost, we deliver 95% of emails within a 1 window).

ii) Real-time Email Performance Data

Real-time email performance data is an incredibly powerful tool that allows you to improve user experience and boost engagement.

For instance, you can:

  • Email product recommendations right after the customer has completed an eCommerce transaction. 
  • Create a dynamic header image that changes depending on when the user opens the email.
  • Design promotional emails where the offer changes based on when the user opens the email. 

When you are exploring real-time data options, verify whether the data provided is actually in real-time or is displayed after a lag. 

iii) Conversion Rate Tracking

Can your mass email service display business goals like revenue, leads and user sign ups against individual email campaigns?

While it may not be able to directly measure these goals because of a lack of tracking pixels, it should still integrate with services like Google Analytics and display those goals right in the email dashboard. 

iv) Access to Email Transaction Logs

Data portability and access should be a critical point in selecting your email service provider. 

While most service providers offer 7-30 days transaction logs, this time window might not be enough for many brands who might send emails once or twice every 15 days.

So here’s what you should look for when evaluating an email service provider on data access:

  • 60- 90 days complete transaction logs
  • An API to automate the data export.

Pepipost offers 90 day transaction logs as download, giving you a long term view of your email performance.

v) Webhooks

Webhooks are a fairly standard feature in mass email services, but not all webhooks are the same.

Since your email service provider doesn't work in isolation, it's important to check whether it provides extensibility with other products in your marketing stack through the use of plugins.

Go to Table of Contents

5. The API/Integration Combination

In 2020, APIs are not just for developers and technically proficient marketers. API/Integration in mass email service

Nontechnical users are also using APIs to extend the functionality of tools in new and innovative ways. 

A site like RapidAPI hosts thousands of free and public APIs that you can either plug into your email campaigns, or with your dashboard to make you a more efficient email marketer.

improving efficiency with APIs

The email tool of your choice should have easy to understand API documentation that can be used ideally by copy-pasting code samples. 

You should also evaluate the number of native integrations with third-party tools and whether your prospective email service provider has a  Zapier integration. 

Different partnerships for Pepipost

Different categories of Pepipost partners

The former is preferable because it’s maintained by the vendor and is usually more reliable and cost effective than the latter.

Factors you Should Consider when Picking Email APIs 

According to Cameron Kane, CEO of enterprise email marketing platform iPost email APIs should be:

  • Scalable
  • Have transparend terms of use
  • The right type (SOAP, RESTful, Synchronous etc)
  • Clear documentation and help with integration
  • Regularly maintained

Let’s drill a bit deeper into the API and integration nice-to-haves.

i) Migration API for Easy Portability

Migrating from one email service provider to another can be anywhere between intimidating and nightmarish. 

You might lose past performance data.

You might have to change multiple settings, test and possibly require developer resources after the switch.

So when you are looking for a change, check whether the prospective service has an easy to deploy migration APIs that can do the heavy lifting for you.

ii) Email Validation APIs

When you have an email list with 1000s, or 10s of 1000s of emails, a percentage of them will be inactive, unreachable or broken.

These email addresses can cause deliverability issues and harm your domain and IP reputation.

It’s essential that your email service provider makes it simple to detect these email addresses so that they can be scrubbed out of your list.

With an email validation API you can extend the validation functionality to webforms, catching invalid addresses at the source instead of letting them clutter up your email list.

email verfication from a form

Neverbounce, a Pepipost partner verifies emails entered in a form, and keeps your list clean

iii) Multi- Lingual Libraries and SDKs

It’s not enough for your email service provider to offer APIs.

They should offer libraries in popular languages like Python, Ruby, C# etc so that your developers can easily incorporate the mass email service with your website or app. 

libraries for email

iv) Extensive Developer Documentation

Developer documentation is also a critical criteria in picking your email tool. 

Extensive documentation is a leading indicator of a service’s commitment to customer success.

If the email service you are evaluating doesn’t have in-depth documentation, your total cost of ownership would skyrocket, even if the startup costs are low.

v) Number of Native Integrations

Native third party integrations are always superior to alternative like integration through Zapier because they are supported by development teams.

Check out blog posts or social media reviews/customer experience on how well these integrations work for the service you are considering. 

Also check out how the level of tech support around integrations provided by your mass email tool- if an integration is broken you must be able to get the issue resolved ASAP.

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6. The Pricing Decision

When you are sending a few thousand emails per month, you don't really need mass email service pricingto think about pricing.

But when you scale your email volume to five or six figures  per month, your email bill can add up fast.

Depending on the choice of your mass email service provider you might have to pay anywhere from a few thousand to tens of thousands of dollars per year extra...

...for the same performance and roughly the same set of features.

Pricing comparison Pepipost vs Sendgrid vs Mailgun vs Sparkpost

Pricing comparison between some mass email service providers

Therefore, it's essential for you to consider pricing at high volumes as one of the variables while making a decision on which mass email service to choose from.

Go to Table of Contents

7. The Security and Compliance Logjam

The final item on your email service wishlist should be about evaluating Security and compliance mass email service toolthe security and compliance requirements of your email service provider. 

A clean and engaged email list is potentially worth multiple times your current revenue.

While it’s absolutely essential that this data be secured, you should also comply with important regulations like GDPR. 

Here are a few things you must consider for keeping your email list secure and compliant:

i) 2 Factor Authentication

2FA is table stakes for any serious email service provider.  

However, the default SMS based 2FA has several security issues including phishing.

If you want to be more secure, look for service providers who offer the option of using an  authentication app like Google Authenticator.

ii) Compliance with GDPR and California Consumer Privacy Act

All legitimate email service providers will be GDPR compliant, but you must look out for how easy is it for you to comply with different requirements of this law. 

Ideally, your service provider should offer a GDPR API so that you can comply with user requests programmatically instead of running manual queries.

You should also check out for compliance (or a path to compliance) with the California Consumer Privacy Act which has already come into effect on Jan 1 2020.

iii) Compliant Data Centers

Even as a small or medium business, you should have secure access to your email data at all times, and it should be stored in compliance with industry standards like SSAE 18 SOC 2 Type II or ISO 27001.

Also check for whether your mass email service provider hosts data across multiple locations and has documented disaster recovery, business continuity, and data backup policies. 

iv) Email Encryption in Transit and at Endpoints

With email involving so many intermediaries, it can be easy for a malicious actor to hack into a weak link and access private data in transit. 

Your email service provider should encrypt email traffic using standard protocols like TLS, while the API endpoints where email  traffic originates or terminates should support HTTPS/TLS.

v) Granular Access Control for Large Teams

When you are working with large teams, not everyone should have the same level of access.

In particular, look for:

  • the types of users you can create with different access permissions
  • ease of adding/deleting new users

Go to Table of Contents

Price vs. Features- How To Best Pick Your Mass Email Service Provider

When you are knee deep in the research process of picking an email service provider, you might be tempted to do a price to price comparison.

And because higher price is usually a signifier of quality, you might pick a more expensive option.

That option will get you more features, but most of them might be ignored.

A Email Vendor Satisfaction Report by Holistic Marketing found that only 30% of users are using 60% or more of their ESP's features.

mass email service vendor satisfaction

Image courtesy Email Vendor Satisfaction Report

Effectivlely, 70% of marketers are paying for features that they will never use.

So what should be the selection criteria for an email service provider?

According to Kath Pay, CEO of Holistic Email Marketing and an email marketing expert:

  • Pick your email service provider according to your overarching business requirements
  • Determine must-have features based on your business goals, and group providers according to budget range
  • Audit your current ESP to determine gaps
  • Get demos, based on a list of your requirements, goals and budget

And while picking the right vendor is important, even more important is to know how to avoid the bad actors.

Marcin Puś, an online marketing expert writes on the red flags:

  • A substandard website
  • A third party SMTP engine, or a reseller
  • Unresponsive to negative public reviews
  • Tiny team, without bench strength in customer support
  • Scanty support documentation
  • Poor deliverability rates

If you follow this guide, and be mindful of the red flags and must-haves, the email service provider shortlist narrows down significantly to 4-5, saving you time and improving the chances that you are picking the right partner.

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