email threading

Stay threaded: How to manage and control email threads

6 min read
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Is there any form of communication more polarizing than email? Some people flock to it as their preferred method of communication – the “this meeting could’ve been an email” crowd. Others succumb to the mass quantity of emails and outright ignore their messages as they unmanageably pile up in their inbox. 

But what all of us can agree on is that email is a crucial, ingrained aspect of how we communicate today – both personally and professionally. While the origins of email date back decades, email as a conversational tool is a relatively new channel that evolved out of necessity due to the explosion of its utility in our everyday lives.

Cut to possibly the most chaotic element of email communication: the email thread. Who among us hasn’t gotten lost in the veritable maze of messages in a single thread, trying to connect the dots to derive a modicum of meaning from this multiverse of madness? And due to its prevalence today, would it surprise you to know that email service providers like Gmail and Outlook don’t actually support email threading natively? (More on that later).

Let’s brave the intricate web of email threading together by looking back on its rise, analyzing the current state of the feature today, and identifying practical solutions you can implement to support, display, and manage these often twisty, tangled threads.

What is email threading?

An email thread is a single email conversation beginning with one email (the start of the conversation) and including all of the subsequent replies and forwards regarding that original email. 

Email threading, then, is essentially a feature that automatically groups related messages together so everyone in that “thread” can see each individual email in the context of a larger conversation.

This feature is an increasingly important way to connect related email messages that may not show up together otherwise. The selling point for this feature is that it groups together relevant messages in one place or “thread” for greater context and ease of review. 

But as our use of email skyrockets – the number of email users in 2021 clocked in at 4.17 billion while American workers received an average of 126 emails a day – email threading is becoming more complex and unmanageable considering its benign origins related to organizational efficiency.

The origins of email threading

Like many predominant aspects of our society today, we can thank the 90s for email threading. The feature first dates back to older email clients like Netscape Mail and Grendel. These clients lacked any conversational information from the IMAP protocol, so they instead inferred it from an email’s metadata or content. The email client, utilizing a complex algorithm, could then aggregate a thread by tracing replies back to their original messages.

It took until 2007 with the public beta launch of Gmail for email threading to really come into its own as a feature. With its “conversation” feature, Gmail introduced the modern day concept of threading and enabled messages in the same thread to appear as one single, collapsable email in inboxes. This was the inflection point for email’s evolution as a communication medium today.

Shortly afterward in 2008, the algorithm that those older 90s email clients used for threading integrated into IMAP as a proposed extension called THREAD. However, most email clients including Gmail and Outlook don’t actually support this extension on their IMAP servers. 

Making things even more complicated, an email doesn’t contain any metadata that outright identifies if it belongs to a thread. This means each email client determines how to display conversational threading without a commonly shared convention on how to treat the quoted messages that ultimately comprise a thread. 

With this variability, it’s almost impossible to teach an email client how to easily recognize where an original email ends and a reply or quoted message begins. Welcome to the threaded madhouse!

Reduce the chaos of email threading with an email API

Because threading is interpreted by the end user interface of the email client you’re using to read it, threading display issues are incredibly common and a frustrating aspect of building an email application or one that supports robust email capabilities. Building a user-friendly email threading feature on your own is a massive undertaking that would require months of developer time and resources.

However, an email API solution can make email threading drastically less convoluted. Take the Nylas Email API, for instance. It’s a single point of integration connecting your app to your users’ inboxes, powering bi-directional email with 99.6% deliverability. A pivotal value add of our API solution on the email read side is that we make email threads easy to deal with by treating them as something that people can actually manipulate in their inboxes.

Nylas threads email messages together using a variety of heuristics. With Gmail and Microsoft Exchange accounts, messages are threaded together as close as possible to their representation in the environments of those email clients. For all other email providers, including generic IMAP, messages are threaded using a custom JWZ-inspired algorithm. 

All emails forwarded to other people in a thread will remain in both the thread on the provider side and Nylas. Actions like archiving or deleting can be done on threads or individual messages. You can even perform bulk operations on all messages in a single thread using a convenient shortcut.

Stay threaded with the Nylas Email API

Nylas is the only bi-directional API solution that supports email threading functionality. Beyond this incredibly valuable add-on, our Email API also helps you easily establish native email integration with all service providers fast and build engaging email features. Whether it’s email authentication, unmatched deliverability, or full CRUD capabilities, our solution will help you stand up these crucial features, saving thousands of developer hours and enabling you to go to market faster.


Learn more about how you can build a threaded email inbox view with the Nylas Email API and then check out how Pipedrive added millions in revenue leveraging our solution.

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