Transactional Email APIs vs Contextual Email APIs

Learn about the differences between SendGrid and MailChimp's APIs vs. Nylas.


Cloud-based email API technology has advanced a long way in the past decade, diversifying substantially in both breadth of functionality and depth of integration. The emergence of email APIs that allow you to embed the inbox into any software application means new ways of building email functionality that can take advantage of the contextual information that lives in those apps.  

In the previous article Intro to Email APIs, we introduced the concepts of an email API and some real-world examples of their usage. In this article, we will dive deeper into the types of Email APIs available for developers, and explore further what it means to be a Contextual Email API. Let’s dive in!

What’s a Transactional Email?

Transactional emails are those emails which are triggered by standard user interactions within an application, such as creating a new account or placing an order on an e-commerce site. Generally speaking, a transaction is an event that involves an exchange between your web/mobile app and the user.

Examples of events that trigger transactional emails include:

  • Email account confirmations
  • Password resets
  • Purchase order confirmations
  • Digital receipts

Transactional emails are typically triggered programmatically via a web API or SMTP relay because they happen frequently as an immediate consequence of predefined user actions. Companies that specialize in transactional emails include SendGrid, MailChimp, and MailGun.

Is Marketing Email the Same as Transactional Email?

Marketing emails operate just like transactional emails, except that instead of being triggered by individual user actions, marketing emails are timed and sent strategically to a specific list of recipients. The content will correspond to marketing campaigns, product promotions, newsletters, or other general communication for customers that does not apply to a particular transaction.

Examples of marketing emails include:

  • Welcome and onboarding drip emails
  • Promotions and coupons
  • Newsletters
  • General announcements

Marketing emails and transactional emails both operate at the same level of depth and differ only in the timing and content of the messages. Most Transactional Email API providers cover marketing email automation use cases just as well as transactional use cases. They’re well suited for either 1-to-1 or 1-to-many email blasts with tokenized customized messaging.

What’s a Contextual Email API?

Contextual Email APIs, in contrast to Transactional and Marketing Email APIs, are designed for developers building software applications that require email sync, send, and analytics embedded directly into the application for their end-user’s benefit. A Contextual API is named such because it lives within the context of a larger application, with direct access to the state of the system and all connected accounts.

Outlook.com, Microsoft Exchange, Office 365, Gmail, and IMAP email providers each have different methods for syncing and sending emails. If you have a user base spread across different email providers and you want to have a unified email experience for your application, you have two choices: build out the necessary integrations to each provider yourself, or integrate with a Contextual Email API provider to abstract away the complexities of building and maintaining each integration. A Contextual Email API allows you to power your web/mobile app with email sync & send across 100% of email providers using just one API rather than several different ones.

Contextual APIs are commonly chosen for applications that need a complete communication and scheduling solution embedded within the app for their users. The creators of these apps want to help their users understand each contact, opportunity, or deal at a glance without worrying too much about the underlying communications architecture.

Common applications include:

  • Customer Relationship Management systems (CRMs) (see case study)
  • Applicant Tracking Software for Recruiters
  • Real Estate Software for Agents to Manage Deals
  • Finance/Fintech Software for Advisors (see case study)
  • Legal Software (see case study)
  • Automotive Software (see example use cases)
  • Productivity Software that has an Email Component

Essentially, any product or service that centers around relationship management with clients or customers would want to leverage a Contextual Email API Platform.

If sales representatives, recruiters, finance and real estate agents don't have to switch to another app to communicate, they can be much more productive and close deals faster.

In many cases, you’ll want to have deeper personalization in your communication with key clients, so contextual APIs are designed with this level of customization in mind. They’re suited to both 1-to-1 and 1-to-many email blasts where personalization is essential to close high-value deals.

Using Contextual Email APIs

Developer-led API companies like Stripe (a payments API for online businesses) and Twilio (APIs for SMS and Video) know first-hand the pain of integrating with multiple, individual APIs and are intentional about making the experience as easy as possible for developers.

The implementation ideology of a Contextual Email API is to help you connect to multiple systems with one integration. That is, to simplify your email integrations into one RESTful API, freeing up your time to build other important features.

Once you’ve integrated with a Contextual Email API and you’re ready to have individual users authenticate their email accounts with your app, specific access tokens give access to individual accounts. The details of the email integration for the host of the mailbox are handled by the intermediary Contextual API, eliminating the need for your team to specialize in securing your integration with each email provider.

With direct access to user’s inboxes via a universal email API, creating products that integrate with and embed email functionality becomes richer and easier to do.

Universal email APIs don’t just save you the initial cost of building the integration. They also help:

  • Reduce ongoing maintenance and support costs: Universal APIs manage all of the ongoing support and maintenance for you. When you integrate with ESPs without the help of a universal API, you’ll find yourself debugging customer issues, managing ESP updates, and diving into edge case issues that arise.

  • Improve the security of your integration: Email APIs transfer a lot of rich data, so they’re secured with some of the strictest standards. Compliance certifications to look for in an API provider include SOC 2 Certification, GDPR Compliance, EU Privacy Shield Certification, and HIPAA and FINRA readiness. As an extra layer of security, API platforms should undergo third-party audits and rigorous penetration tests.

  • Reduce costs over time: Ongoing costs include headcount for ongoing maintenance and support, server costs, and security costs. Attaining industry-standard security certifications like SOC 2 runs an additional $20,000-$30,000 for the most basic certification.

At Nylas, we’ve built a contextual email API with all of these features and more. Our API allows you to quickly integrate with every email service provider in just a few lines of code, and our API success metrics speak for themselves:

  • 99.9% uptime
  • P90 response time <500ms
  • Encrypted credentials
  • Token management
  • OAuth2 support for Google (with Microsoft support coming soon!)
  • Selective sync and authentication scopes
  • Customizable native authentication
  • Annual third-party audits for network, application and corporate security

Integrate email with confidence, and focus on building the features you love.

Get a free API key and test out Nylas’s Universal Email API by creating an account here: https://dashboard.nylas.com/register

Now that you’re familiar with Transactional/Marketing Email API use cases and Contextual Email API use cases. Nice! Each type of API is perfectly suited to its specialization and passes value on to the developer in a different way. Check out our infographic for a visual summary of everything we covered here.

Next up: Web API vs SMTP Relay! Going back to the Simple Mail Transfer Protocol that makes this all possible.

About Author

Tasia Potasinski

Tasia is the Head of Marketing at Nylas. In her free time, she enjoys discovering new running trails in the Marin Headlands and exploring the best vegan bakeries in San Francisco.

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