Slack vs Email: When to Use Them?

Slack and email are probably two of the most popular communication tools used by businesses today. As of January 2019, Slack had 10 million active users using its platform. The media branded them early on as the "email killer".

This framing touched on people’s anxiety; it hit a nerve. People were drowned by hundreds/thousands of emails in their inboxes and they needed a fix. Slack was the fix. But it came with a hidden cost.

Should you stop embracing emails altogether? Probably not. Email is still the most popular form of communication with an estimated 319.6 billion emails sent and received daily around the world in 2021.

Problems that are being solved by Slack don't render emails useless, it's quite the opposite. Both are evolving with different a purpose.

What's the Difference Between Slack and Email?

Emails are a great tool for one-to-one communication, but it’s not very friendly to large groups of people. As a result, many businesses have moved on to more modern alternatives like Slack. But what exactly is Slack and how does it differ from email?

The key difference between Slack and email is that Slack is a team collaboration app and traditionally email is an individual communication tool.

What Is Slack?

Slack is a channel-based team messaging app. You create broad channels (General, Sales, Development, HR, etc.) where your team(s) can discuss. Those channels are long-lived and infinite, meaning older messages move up as soon as new messages are posted. Thus Slack is synchronous, it’s best to consume new messages as soon as they are sent, or else you might miss some important content.

Slack responded to those shortcomings by releasing a feature named Threads. They let you start sub-threads inside channels. You can peak at Slack's message threads FAQ entry to understand how they work (not simple).

Missive conversations are composed of either email or chat messages
Use threads… but don’t if it’s important.

What Is Email?

Email is an asynchronous communication method. It’s not real-time like Slack or chat but rather a record of conversations between people over time.

Email is much more than just text messaging; it’s a way of sending files and attachments across the internet with ease. It allows you to send information quickly and cheaply across any distance while still allowing the recipient to reply at their leisure. That makes email ideal for sending data that needs time to process or review before responding.

One of the main differentiators for most businesses is that emails are usually used for external communication as for slack is preferred for internal.

Is Slack Better Than Email?

Using emails for internal communication is slow, noisy and cumbersome. Slack, with its friendly chat messaging UI and branding, brought a silver lining for many organizations who were looking for a better solution.

When the media says Slack is an email killer, what they are not saying is that it’s killing email for internal team discussions only. It’s not killing email for external communication. All organizations using Slack still exchange hundreds or thousands of emails a day with customers/prospects/partners/providers and whatnot.

When moving internal communication away from email to Slack, a second silo of vital information is created.

Slack creates a new silo of vital information

Slack vs Email: Pros and Cons

Having a second communication silo comes with advantages and inconveniences.

What Are the Advantages of Slack Over Email?

With remote working becoming more and more prominent, Slack poses certain benefits to teams by providing a virtual HQ where they can have the conversations they would normally have in real life.

The channels and DM make it particularly useful for teams to have no related work discussion in a more casual channel while having channels dedicated to the different teams of projects. It's an excellent way to have real-time and ad-hoc communication around internal projects or tasks.

What Are the Disadvantages of Using Slack Over Email?

The problems of Slack come up when trying to exchange emails or communicate with external parties. It’s now harder to search for all relevant conversations related to a project because some will be external in emails and others internal in Slack. Internal conversations related to external factors also lose context. For example, you could receive an email from a partner asking to change the terms of your partnership. You want to consult your teammates before agreeing, so you start chatting in Slack about the legitimacy of the requested changes. A heated debate ensues.

When using Slack, internal discussions are separated from external ones.

Both the internal debate and the external conversation with the partner will sit isolated in their own silo. Don’t get us wrong here, Slack is a great improvement compared to the era where email threads were composed of both internal and external conversations. However, it’s definitely not perfect: losing context and spreading information in two silos comes with a big cost to productivity. Not to mention the need to go back and forth between multiple apps only to gather all the information in one place in the end.

In Missive, everything external is email, everything internal is chat. Both are merged in unified conversations.

In the above scenario, you and your team would discuss the proposed partnership changes right in the context of the email using chat.
Slack Email
Pros 👍 Cons 👎 Pros 👍 Cons 👎
Conversations can be separated into channels. Free version only comes with 90 days of history. Truly enables asynchronous communication. Without Missive, team collaboration is almost impossible.
Scope of conversations can be defined as private, shared with certain people, or public. Can easily be overwhelmed by too many messages. Can be used with anyone (Who doesn't have at least one email address these days?). Email threads can be hard to follow and don't provide a way to reply to specific people.
Make real-time collaboration with colleagues easier. Messages can feel disorganized and hard to follow, Can be used to send messages to multiple people inside and outside of the organization.
Have chat, audio, and video call features. Notifications can quickly become annoying Can be used to send photos, files, and any other attachment.
Offers many integrations for a better workflow. Can't be used to communicate with someone that isn't on Slack. Most people already used it and are familiar with it.

Missive: The Way Emails Should Be

Slack certainly solves a few of the problems of the way most of us are dealing with emails, however, better tools could make emails more efficient especially when collaboration is needed.

Time to meet Missive!

Missive is conversation/thread-based like virtually all email clients. Conversations can contain emails, chat messages, or a mix of both.

In Missive chat and email conversations are in one place.

That's where the beauty of Missive is: email collaboration. No more back and forth between your email client app and your internal messaging app to collaborate with your coworkers on an email or forwarding an email to your colleague and then pinging him on Slack to ask for his opinion. Everything happens inside Missive.

Internal chat screenshot

In the left column of the Missive app you can see something not found in an email client: Pins. Similar to Slack channels, Missive automatically creates a general room for your organization as well as 1-to-1 private rooms between each team member. These will be pinned by default, but you can also pin any email and/or chat conversations you have.

Pins are a great way to keep important conversations handy. They will stay right where you put them, contrary to your Inbox where new conversations will push older ones down.

Missive also offers the ability to create tasks in any conversation and a task can be assigned to one or multiple people. A lot of our daily tasks are generated from the interactions we have with the outside world (emails) and the discussions we have internally (chats). In Missive, a task is simply a comment with a checkbox.

Slack doesn’t offer any task or assignment features, although it does offer integrations with many task management apps and SaaS providers. Missive also has integrations with several popular products.

With Missive, you can replace both your email client and chat application for internal and external communication, meaning it’s one less tool to get familiar with, keep open and monitor.

When to Use Slack vs Email?

Slack and email are two of the most popular tools for communication in the workplace. Both tools have their pros and cons, but each has a specific purpose. Here’s how to know when to use each one:


Email is the best tool for sending messages that need to be read at a later date or by multiple people. For example, if you want to send an important memo or report, email is the way to go because it gives your recipient time to read it when they have time and aren’t distracted by other work tasks.


Slack is a great tool for sending messages that don’t require reading at a later date or by multiple people. For example, if you want to ask your coworker about a meeting time or tell another coworker how much fun last night was, Slack is a great option because it allows you to communicate quickly with just one person without cluttering up everyone else’s inboxes with unnecessary messages.

Check out how Missive compares to Front app, Missive compares to Spark, Missive compares to Outpost.