Slack vs Email - Talking To Your Customers

Discover the key differences between Slack and email as collaborative tools, exploring their impacts on workplace communication, productivity, and the evolving needs of modern business environments.
Dominic Kent
Dominic Kent is a content marketer specializing in unified communications and contact centers.
Slack vs Email

Slack vs Email. The age-old debate that has rolled on and on since, well since Slack launched.

Often touted the email killer, Slack has recently pivoted to labeling itself as the internal email replacement.

We know Slack is one of the most popular collaboration tools on the market for internal communications, but when it comes to external comms, we often resort back to email.

In this post, we look at why our behavior is what it is and learn if Slack vs Email will ever have an outright winner.

Table of Contents

  1. Why do people prefer Slack?
  2. When to use Slack vs Email?
  3. Intracompany Collaboration
  4. Intercompany Collaboration
  5. Slack vs Email: Pros and Cons
  6. Can Slack Replace Email?
  7. Alternatives to Email in the Workplace

Why do people prefer Slack?

When you ask why do people prefer Slack, you'll get a variety of answers.

Some are simple.

In the age of "always-on" communication, reacting to messages is often easier than typing out that you've understood something. And when you've worked with the same coworkers for a period of time, they'll immediately know that your ✔️ emoji means you've actioned the task they messaged about.

Why do people prefer Slack?

Some revolve around etiquette. How many times per day so you think heavy email users type "Hi Dominic, hope you are well" or "hope to hear from you soon"?

You wouldn't start a conversation this way in the office, so why do so on email?

The use of channels and message threads is a big reason people prefer Slack to email. Who wouldn't want organization over communication chaos?

Recognizing the benefits of Slack, companies spend more time in Slack than they do checking and responding to emails.

So even new users of Slack are happy to adopt Slack over email.

Slack also thrives off niche use cases like community workspaces and breakout areas like group DMs.

Araminta runs a fintech marketing agency but leverages content marketing communities for collaboration and advice from peers and mentors.

When to use Slack vs Email?

Traditionally, there are two types of communication within a business:

  • Intracompany collaboration
  • Intercompany collaboration

Intracompany Collaboration

Intracompany collaboration is when you message your colleagues within the same company.

Your peers likely use the same Slack workspace and all your employees have a Slack account.

In the left-hand pane of your Slack workspace, you have a list of channels and the option to start or continue a direct message (DM) with anyone in your company.

This can be both one-to-one messages or group messages.

You can see below, I regularly message Jennifer on a one-to-one basis. Further down, you will see I often message Meredith and Tom together in a group message.

When your entire organization (or the people you regularly message) uses Slack in the same workspace, the need for one-to-one and group email becomes near redundant.

Everything you need to say via email can be communicated within a Slack DM.

For internal project work, Slack introduced channels to the world of collaboration.

As you see below, every topic of group conversations I have is contained within the Channels section.

This removes the need for me to ever send a "group email" and means everybody can respond in one place, with the ability to neatly organize responses via threads.

So, if everyone inside your organization uses Slack to chat, Slack's ambition to be the internal email replacement is almost complete.

But what if not everyone inside your organization is a Slack user? After all, 91% of businesses use at least 2 messaging apps.

Is the only solution to toggle between apps just to keep up?  

The best solution for intracompany collaboration

Mio bridges messages from Slack to Microsoft Teams, Webex, and Zoom Team Chat.

You can stay in Slack and send messages to your colleagues that use Microsoft Teams or Webex.

They stay in their platform too and Mio translates the messages across platform.

And it’s not just messages that are supported! GIFs, emojis, channels, and message edits/deletes are all supported.

If this sounds like something you need, learn more here.

Intercompany Collaboration

Intercompany collaboration is when people within different organizations need to collaborate with each other.

Luckily, Slack introduced Slack Connect in 2020.

Slack connect allows you to create a channel and allow another organization to collaborate with you. Both parties stay in their respective Slack workspaces and communicate without having to switch between multiple workspaces.

This feature takes the principle of a shared channel and allows you to connect to up to 20 organizations per channel.

Slack vs Email: Pros and Cons

When searching for advantages over Slack over email, you could find yourself in a list of features that probably doesn't mean a lot unless you're already using Slack.

Google also tells us there are over 7 million results for this query so let me save you the time.

Advantages of Slack vs Email

Slack Pros vs Email

I've rounded up the most popular suggestions for advantages of Slack vs email...

  1. Slack houses both synchronous and asynchronous conversations in the same place - you can use Slack as an IM for immediate responses but also leave something to come back to at a later date.
  2. There's no chance of accidentally deleting an important email - as persistent chat, the entire Slack thread of conversation remains available.
  3. Channels provide areas for your conversation topics to be broken down into - save you searching for that specific email at the last minute.
  4. Rapid communications enable the ability to come together as a team and brainstorm anywhere and at any time.
  5. While email integrations exist, the number of Slack integrations now far exceeds the amount you can integrate with email.

You may also like: Top 43 Best Slack Integrations, Apps, and Bots for 2021

These are only the most commonly suggested advantages of Slack over email.

Slack customization

As you start to use Slack, you can customize your workspace to the way you work.

If you chat with someone constantly, you might want to "star" the conversation so it appears at the top of your Slack workspace.

See below where I have starred a channel, a multi-party conversation, and two direct messages that are either my most used or most important. Starring a message moves these to the top of your channels and messages.

Slack as a hub for work

The most distinguishing advantage of Slack over email is that everything (okay almost everything) is - or can be - in one UI.

When your work hub is your email client, you forever switch between your chat tool, your telephone, and your meetings platform.

With Slack, all your messages are in the same UI and have quick access to a whole host of communication and collaboration features are literally at your fingertips.

Outside of the functionality that Slack provides, there are some more strategic advantages that Slack provides over email...

Slack as the expected tool of choice

Attracting talent in 2021 is different to attracting talent when email was revolutionary.

If you want to hire the best staff, you need to provide the tools they want to use.

For example, hiring a marketing professional who thrives with productivity tools would be counterintuitive if you force them to use email to collaborate with colleagues and contractors.

According to the Office Hours blog, Slack is best when:

  • You need a quick answer on something simple
  • If you want to share & collaborate on something in real-time
  • If you need an immediate response

Only yesterday, I was sat in a coffee shop working with a friend that works at another company who was criticized for not responding to an email quickly enough.

Email is not the appropriate tool here.

Slack Cons vs Email

In certain scenarios, the cons of Slack vs Email rear their head. Let's address those here.

Everybody is let loose to do their own thing

Without appropriate guidelines, Slack users could be subject to notification overload.

For example, it is common practice to start a thread when replying to someone's post in a channel. This way you don't interrupt everyone in the channel - and it's obvious you are still referring to the topic outlined in the initial post.

Below you can see where Rebekah asked about a specific article she was helping with and we discussed in the thread as replies.

I then start another conversation in this channel about the plan for next week so nobody could get the context of the conversation confused.

Not everyone is on Slack

The most obvious con of using Slack as an email replacement is that not everyone uses Slack.

When colleagues use other team collaboration platforms - like Google Chat or Microsoft Teams - staying in Slack feels impossible.

But that's where Mio comes in.

When you want to use Slack, but your teammates prefer Google Chat, Microsoft Teams, Webex, or Zoom Team Chat, save yourself from dropping what you are doing and moving over to another platform.

Mio enables you to stay in Slack and chat to your colleagues as if they were on Slack.

The best part? They stay in their chat app too.

Mio translates the messages from one platform to the other so you don't need to resort to email or set up a conference call.

If you want to stay in Slack instead of resorting to email, learn more here.

Can Slack Replace Email?

Slack has changed its own branding from email killer to internal email replacement.

Slack itself requires an email address to first sign into a Slack workspace. So killing email would require Slack to replace the entire "login with email" element of their own tool.

Such a change would cause an unthinkable amount of change in the way people login to apps, websites, and even hardware that the email address will seemingly never die.

However, replacing the practice of sending an email isn't impossible.

But it is still a long way away.

When I spoke to Robert Vis, CEO of MessageBird in early 2019, he told me:

"The legacy that email will have is huge and the reality is that email is sometimes efficient. Maybe in a millennial world, everybody is texting five, six, seven words. But, we need to cater for all personas and email is still high on the list for a lot of people."

Little has changed in a year. The people inside and outside your business that prefer email still prefer email.

The barrier to replacing the process of sending an email could be replaced by team collaboration apps - rather than just by Slack.

I am on the side of team collaboration. For me, email is clunky. I celebrate a small volume of emails when I wake up and check my phone.

If your customers are using other apps like Microsoft Teams, convincing them to move to Slack so they can chat with you is unlikely.

The compromise can only be one of two things:

  1. Resort back to email for asynchronous external communications
  2. Allow your customers to use their team collaboration platform of choice and connect to them through a federation service like Mio

You may also like: 6 Ways to Connect Slack and Microsoft Teams

Alternatives to Email in the Workplace

I reached out to my network to see what everyone else was using, other than Slack or email, for external collaboration.

I asked: What Happens When You Need To Chat Externally?

Sunny Dhami, Director of Product Marketing at RingCentral, said it's about how you manage this as a business.

"Some collaboration tools do give you the ability to add guests and collaborate with them within the tool but it’s all dependent on how the business wants to engage with external contacts. I use a mix of both, depending on the outcome I’d like to achieve."

Tom Arbuthnot, Principal Solutions Architect at Modality Systems, said it depends on the external party's culture and who has the "power" in the relationship.

"In our case, if a customer is on the same platform or has access, that’s great. If not, email is the common denominator. Using email 'sometimes' doesn’t mean no use case for team chat."

Karoliina Kettukari, Senior Consultant at Sulava, mentioned her experience in Microsoft Teams - seemingly Slack's largest competitor.

"If it's a project, we have a common workspace with other parties. If it's a limited number of single messages we need to exchange then e-mail and phone will do. Depending on federation policies, Teams chat may work too."

April Diehl, Network Engineer at Spectrum Enterprise mentioned how useful Skype for Business federation was when collaborating externally.

"In many cases I use Skype for Business with customers who also have Skype open to external contacts. I have used Slack in the past with customers and it is great because it tracks the conversation and you can upload documents to it as needed. Email works but keeping track of the conversation if there are multiple threads is cumbersome."


Email is unlikely to disappear any time soon.

That doesn't mean you must remain totally loyal to it. And, in most cases, you are doing your team collaboration tools a disservice.

The reality is that most of your contacts probably have a team collaboration tool.

If they use Slack too, Slack's shared channels feature is perfect for this.

If they don't use Slack, it's not the end of the world.

Email will always be there. But the more productive method is for you to stay in Slack and your customers to stay right where they are.

Final Words

Does your enterprise use multiple chat platforms?

Do you prefer Slack and struggle to maintain smooth communication with your colleagues on different chat apps?

If the answer is yes to both questions, according to research, they’ll likely be using Microsoft Teams or Cisco Webex Teams.

When this is the case, you don't have to resort to email.

Mio bridges the gap between Slack and Microsoft Teams, Webex, or Zoom Team Chat…

You can stay in Slack, leave email well alone, and send messages to your colleagues on other platforms.

They stay in their platform too and Mio translates the messages across platform.

And it’s not just messages that are supported! GIFs, emojis, channels, DMs, and message edits/deletes are all supported.

If this sounds like something you need, learn more here.

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