Kolab
Kolab: A broad open-source mail and collaboration suite for teams managing their own infrastructure. Ranked #14 of 34 in Mail Server Software by our editors (7.8/10); pricing: Free plan; best for open-source mail with collaboration tools.
At a glance
- Editor score7.8 / 10
- PricingFree plan
- Best forOpen-source mail with collaboration tools
- Free planYes
- Paid fromFree
- Facts checked20 Sep 2026
Where it wins
- Combines email, calendars, tasks, contacts, and shared resources
- Supports IMAP, SMTP, ActiveSync, CalDAV, and CardDAV
- Includes spam filtering, virus scanning, and email authentication support
Where it doesn't
- Self-hosted deployment requires your own infrastructure
- Mobile access relies on third-party apps
- Not suited to buyers seeking a managed hosted mail plan
Our verdict on Kolab
Kolab is an open-source communication and collaboration suite for organizations, families, and teams that want to operate their own email and groupware infrastructure. Its scope extends beyond webmail: users can work with calendars, tasks, contacts, file storage, video conferencing, and collaborative document editing. Access is available through the web, self-hosted deployments, Linux, iOS, and Android, with standards-based support for IMAP, SMTP, ActiveSync, CalDAV, and CardDAV. It is best suited to buyers who want control over their mail environment and need shared productivity features alongside email.
The platform’s main strength is its breadth of collaboration features and client compatibility. Shared folders and calendars support group work, while user aliases, signatures, spam filtering, virus scanning, and support for DKIM, DMARC, and SPF address common mail-management needs. Kolab also integrates with Thunderbird, Outlook, eM Client, Apple Mail, and Apple Calendar. That combination gives organizations several ways to connect existing desktop and mobile workflows rather than relying only on the webmail client.
Kolab’s open-source, free model fits teams prepared to manage their own deployment, configuration, and ongoing infrastructure. The self-hosted approach offers a better fit for organizations that prioritize operational control over a managed service experience. Mobile coverage is available through third-party apps, and buyers should account for that when planning user access. Choose Kolab when a single system for standards-based email, groupware, and collaboration is more important than turnkey hosting. Buyers seeking a provider-managed mail service or first-party mobile applications should consider a different type of product.
Your product? Our editors can test Kolab in depth and publish a review, labelled as paid · from $149/mo →
Kolab pricing
Kolab fact sheet
| Free plan | Yes |
|---|---|
| Paid from | Free |
| License model | Not verified |
| Webmail interface | Not verified |
| IMAP/POP3 access | Not verified |
| Mobile sync | Not verified |
| Antispam tools | Not verified |
| Mailbox limit | Not verified |
| High availability | Not verified |
| Deployment | Self-hosted |
| Platforms | Web, Linux, iOS, Android |
| Compliance & security | GDPR, PCI DSS, 2FA |
| Support | Docs |
| Built for | Small business, Mid-market, Enterprise (editorial estimate) |
| Integrations | 5 integrations: Thunderbird, Outlook, eM Client, Apple Mail, Apple Calendar |
| Pricing | Free plan |
| Website | kolab.org |
| Facts checked | 20 Sep 2026 |
Kolab integrations
Kolab lists 5 integrations on its own site.
- Thunderbird
- Outlook
- eM Client
- Apple Mail
- Apple Calendar
Alternatives to Kolab
- Microsoft Exchange OnlineA Microsoft-centric hosted mailbox service with Outlook, archiving, compliance, and migration tools.9.3
- Zimbra CollaborationA broad open-source suite for organizations that need email, collaboration, and deployment control.9.1
- IceWarpA broad hosted email suite with collaboration, migration tools, and self-hosted deployment.9.0
Also Ranked In
Kolab is ranked in 2 of our directories.
Used Kolab? Be the first to review it
The editor score above is our own research. What this page doesn't have yet is a reader's view — what you used Kolab for, what worked and what didn't. No stars are seeded and no review is paid for; an editor reads every one before it appears.
Write a reviewTwo minutes · verified accounts only · read by an editor before it appears
Featured on iTechGuides
Kolab is listed in our Mail Server Software directory. Add the badge to your site — it links back to this page.
<a href="https://www.itechguides.com/products/kolab/"><img src="https://www.itechguides.com/best/badge/kolab.svg" alt="Featured on iTechGuides" width="230" height="46"></a>
Reviewed by iTechGuides Editors · Editorial team · Updated Oct 2026
Advertiser disclosure: iTechGuides is reader-supported. Vendors can pay for top positions in our rankings and for a place on other products' pages, and we may earn a commission when you click some links. Bought places stand at the number bought; this page and our disclosure say so. Paying vendors may get a fuller, more detailed review from our editors, and that review can change their score. How we rank.
Last updated · How we research and update