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Best Microsoft 365 Alternatives in 2026

Based on real usage data from 0 websites analyzed by StackSee

We analyzed real website data to find the most popular alternatives to Microsoft 365. Microsoft 365 is microsoft 365 is a line of subscription services offered by Microsoft as part of the Microsoft Office product line. See which tools teams actually use instead, backed by real-time detection data.

Top Alternatives to Microsoft 365

Technologies in the Webmail category that teams use instead of Microsoft 365, ranked by adoption.

1

CR

CrossBox CrossBox is a webmail client.

Webmail

2

AP

Apple iCloud Mail Apple iCloud Mail is a webmail service provided by Apple, Inc.

Webmail

3

GO

Google Workspace Google Workspace, formerly G Suite, is a collection of cloud computing, productivity and collaboration tools.

WebmailEmail

4

PR

Proton Mail Proton Mail is the world’s largest secure email service with over 70 million users. Available on Web, iOS, Android, and desktop. Protected by Swiss privacy law.

Webmail

5

OP

Open-Xchange App Suite Open-Xchange is a web-based communication, collaboration and office productivity software suite.

WebmailEmail

6

OU

Outlook Web App Outlook on the web is an information manager web app. It includes a web-based email client, a calendar tool, a contact manager, and a task manager.

Webmail

7

RA

RainLoop RainLoop is a web-based email client.

Webmail

8

RO

RoundCube RoundCube is free and open-source web-based IMAP email client.

Webmail

9

SQ

SquirrelMail SquirrelMail is an open-source web-mail package that is based on PHP language. It provides a web-based-email client and a proxy server for IMAP protocol.

Webmail

10

SY

Sympa Sympa is an open-source mailing list management (MLM) software.

Webmail

11

ZI

Zimbra Zimbra is a provider of open-source email and collaboration software, offering solutions for email, calendar, contacts, and collaboration for both individual and enterprise use.

Webmail