About 21; min
Slack Connect lets you chat with external partners in shared channels. Microsoft Teams offers similar external collaboration through guest access and shared channels. But most companies don’t need either — they need a lightweight way to communicate with clients without adding them to their internal workspace.
We compared Slack and Teams pricing specifically for external collaboration, plus alternatives like Discord and Lark that handle cross-company communication at lower cost.
External Collaboration Pricing
| Feature | Slack | Microsoft Teams | Discord |
|---|---|---|---|
| Internal messaging | Free (90-day history) | Free (with Microsoft 365) | Free (unlimited history) |
| External shared channels | Pro ($8.75/user) or Business+ ($12.50) | Teams Essentials ($4/user) or M365 | Free (server invites) |
| Guest access | Free (limited), Pro+ for full | Included in all paid plans | Free (role-based) |
| Video calls with external | Huddles (Pro+) | Free (up to 60 min, 100 people) | Free (unlimited) |
| File sharing limit | Free: no uploads, Pro: 10 GB/user | 10 GB/user (M365) | Free: 25 MB, Nitro: 500 MB |
Slack Pricing for External Collaboration
Slack Connect — the feature that lets you create shared channels with external companies — requires both sides to have paid Slack plans. If your client uses Slack Free, you can’t create a shared channel with them. This limits adoption in practice: many external partners aren’t on paid Slack plans.
The workaround: Slack Connect DMs (available on Pro) let you message individuals at other companies without shared channels. This covers most client communication needs without requiring the $12.50 Business+ plan.
The Real Cost of Slack for Agency-Client Communication
An agency with 15 internal users on Slack Pro: $131.25/month. Each client they want in a shared channel needs their own paid Slack workspace. If 5 clients each have 3 people on Slack Pro: that’s $131.25 in client-side costs that the agency often ends up subsidizing or the client resists paying.
This friction is why many agencies use separate tools for client communication instead of Slack Connect.
Microsoft Teams Pricing
Teams has a built-in advantage for external collaboration: guest access is free on all paid plans. Add any external email as a guest to your Teams channels — they don’t need their own Microsoft subscription. The guest joins through a browser with no software install required.
For companies already paying for Microsoft 365 ($6+/user), Teams external collaboration costs nothing extra. Compare that to Slack’s $8.75–$12.50/user requirement for Slack Connect.
Teams Guest Access vs Slack Connect
| Aspect | Slack Connect | Teams Guest Access |
|---|---|---|
| External user cost | Must have paid Slack plan | Free (no Microsoft license needed) |
| Setup friction | High (both sides need paid Slack) | Low (invite via email) |
| Security controls | Limited on channel level | Full admin controls (data loss prevention, conditional access) |
| File sharing | Files in Slack | Files in SharePoint (version control, permissions) |
| UX for external users | Good (familiar Slack) | Decent (browser-based Teams) |
| Compliance | Business+ for exports | Included in M365 Business |
Discord: The Free Alternative
Discord offers unlimited servers, channels, message history, and voice calls for free. External collaboration is simple: create a server, invite your clients with a link, assign roles for permissions. No paid plan required on either side.
The trade-off: professional perception. Some enterprise clients won’t take a Discord invite seriously. For tech companies, startups, and creative agencies, Discord works well. For Fortune 500 client communication, stick with Slack or Teams.
Discord for Business: What Works
- Developer communities: Open-source projects, API support, and developer relations all work brilliantly on Discord
- Startup-to-startup collaboration: Tech-savvy partners are comfortable on Discord
- Agency + tech clients: Design agencies working with SaaS companies can use Discord channels per client
- Community-driven support: Combine customer support with community building in one platform
Cost Comparison: Agency with 15 Staff + 10 Client Organizations
| Platform | Internal Cost (15 staff) | External Cost (10 clients) | Total Monthly | Annual |
|---|---|---|---|---|
| Slack Business+ | $187.50 | Clients pay their own Slack | $187.50+ | $2,250+ |
| Slack Pro (DMs only) | $131.25 | Clients pay their own Slack | $131.25+ | $1,575+ |
| Teams (M365 Business Basic) | $90 | $0 (guest access free) | $90 | $1,080 |
| Discord | $0 | $0 | $0 | $0 |
Teams saves $1,170/year over Slack Pro for the same agency. Discord saves $2,250/year over Slack Business+. The cost difference is significant for small agencies where communication tools are a measurable percentage of operating expenses.
Other Options Worth Considering
| Tool | Price | Best For |
|---|---|---|
| Lark | Free (50 users) / $12/user | All-in-one (chat + docs + video + calendar) for cross-border teams |
| Twist | Free (limited) / $8/user | Async-first communication (threads over channels) |
| Rocket.Chat | Free (self-hosted) | Self-hosted Slack alternative with federation for cross-org chat |
| Basecamp | $15/user/mo (flat) | Client projects with built-in messaging, files, and to-dos |
Basecamp deserves mention for agency-client work: $15/user for internal staff, free guest access for unlimited clients. Each project gets its own message board, file storage, and task list. It’s not a chat tool — it’s async-first — but for agencies managing client projects, it replaces both Slack and a project management tool.
Who Should Pick What
Pick Slack If:
- Your team already uses Slack and your external partners do too
- Real-time chat is your primary communication mode (not async)
- The integration library (2,400+ apps) matters for your workflow
- You need Slack Connect shared channels for deep partner collaboration
Pick Microsoft Teams If:
- Your organization uses Microsoft 365 (Teams is essentially free)
- Free guest access for external users is important
- Video meetings are a major part of your collaboration
- Enterprise security and compliance (DLP, conditional access) are required
Pick Discord If:
- Budget is $0 and you need unlimited everything
- Your partners are tech-savvy and won’t blink at a Discord invite
- You want to combine community management with client communication
- Voice channels (always-on office audio) appeal to your remote team
Pick Basecamp If:
- You’re an agency managing distinct client projects
- Async communication (message boards) beats real-time chat for your workflow
- Free unlimited client access makes the $15/user internal cost worthwhile
Best for enterprise external collaboration: Microsoft Teams — free guest access, security controls, and SharePoint file management. The lowest-friction option when external partners don’t have matching software.
Best for tech-savvy teams on a budget: Discord — unlimited everything at $0. The professional perception issue is real but shrinking as more companies adopt Discord for business.
Best real-time chat experience: Slack — the UX, integrations, and notification controls are still the gold standard. Worth paying for if your team lives in chat 8 hours a day.
Best for agency-client projects: Basecamp — project-based communication with free client access replaces both Slack and a separate PM tool.
FAQ
Can Slack Connect work if the other company uses Teams?
No. Slack Connect only works between Slack workspaces. If your partner uses Teams, you’d need to use email, a shared project tool (Basecamp, Asana), or convince one side to switch platforms.
Is Discord secure enough for business use?
Discord uses end-to-end encryption for voice and applies TLS for messages in transit. It’s not SOC2 certified and doesn’t offer enterprise admin controls, DLP, or audit logging. For regulated industries, Discord is insufficient. For most small businesses and tech companies, it’s adequate.
Can I use Teams without Microsoft 365?
Yes. Teams Essentials ($4/user/month) is a standalone plan without Office apps, Exchange email, or SharePoint. You get Teams meetings, chat, and 10 GB storage. For teams that only need Teams, this saves $2/user vs Microsoft 365 Business Basic.
What about email? Is it dead for external communication?
Not at all. Email remains the universal standard for formal external communication. Chat tools supplement email for ongoing relationships where real-time or frequent async communication is needed. Use email for first contact, contracts, and formal updates. Use chat for day-to-day collaboration once a relationship is established.
