5 Best Free Open Source Outlook Alternative Software For Windows

Here is a list of best free open source Outlook alternative software for Windows. Microsoft Outlook is a popular email client software through which users can send/ receive emails, manage emails, schedule tasks on the calendar, etc. These open source Outlook alternative software works similar to Outlook and offers all the primary features like Email management, Send/ Recieve Emails, etc. In addition to that, users can also access and edit the source code of these alternatives without any restriction.

These alternatives offer all the essential email features like compose emails, reply to emails, forward emails, inbox, trash emails, etc. Plus, advanced search and filter features to quickly locate desired emails are also present. Similar to Outlook, most alternatives also offer features like Calendar (to create and view appointments and tasks), Address Book (to manage contacts of users), etc.

Using these Outlook alternatives, users can quickly access and manage one or more email accounts. Plus, these alternatives store all emails locally that users can access even in the absence of the internet. In some alternatives, users can also add accounts of different email services like Gmail, Outlook, Hotmail, etc. These email clients also come with some useful additional features such as Password Manager, Browser, Offline Mode, etc. Go through the list to know more about these software.

My Favorite Open Source Outlook Alternative Software For Windows:

Thunderbird is my favorite software because it is closest to Outlook in terms of features. In this alternative users get all the essential email client, task scheduling on a calendar, etc., features similar to Outlook.

You can also check out lists of best free Open Source Dreamweaver Alternative, Open Source Zoom Alternative, and Open Source Lightroom Alternative software for Windows.

Thunderbird

Thunderbird is a free open source Outlook alternative software for Windows. Similar to Outlook, this software also lets users send/ receive emails, manage calendars, store contacts, and more. Plus, it also lets users open up the calendar, inbox, tasks, schedules, etc., at a time on its multi-tab interface. In it, users can also maintain multiple email accounts. Now, check out the main features of this open source Outlook alternative.

Main Features:

• Inbox: This alternative provides all necessary email features under its Inbox tab. Some of the features that users can access from its Inbox tab are emails and messages of all your accounts, drafts, sent emails, trash, and outbox emails. Plus, features to compose new emails, reply mail, and forward email are also provided by it.
• Search and Sort Emails: To find emails, this software provides multiple search and sort features like Quick Filter (to filter emails based on contacts, tags, attachments, starred, etc.), Standard Search (to search mail by using a keyword or phrase), and Filter Search (it lets you only search the filtered emails).
• Open In Conversation: It is basically an inbuilt chat feature through which users can communicate with each other without sending emails.
• Calendar: In it, you can view all your scheduled tasks and other associated information.

Additional Features:

• Offline Mode: Use it to completely disconnect this software from the internet.
• Add-ons: This software also supports add-ons, using which users can add new features to this software.

Final Thoughts:

It is one of the best free open source Outlook alternative software that provides almost all the email management and Calendar features that you get in Outlook.

SeaMonkey

SeaMonkey is another free open source Outlook alternative software for Windows, macOS, and Linux. It is mainly an email client software similar to Outlook. Plus it also offers tools to manage newsgroup, stored emails, maintain multiple user profiles, and more. In it, users get all the essential email functionality as well such as compose mail, inbox, draft, outbox, etc., features. Now, let’s take a look at the primary features of this Outlook alternative.

Main Features:

• Main & Newsgroup Section: In this section, users get essential email client features like Compose, Get Message, Inbox, Draft, Sent, Reply, Reply All, Mark, etc. In addition to that, advanced search and sorting features are also present in it to locate saved mails.
• Events and Tasks: Using it, users can create and schedule tasks and events. A side Event panel consisting of events and their scheduled dates is also present in it.
• Sync: Using this feature, users can synchronize all their mails and other settings with multiple SeaMonkey software. To perform synchronization, users need to create a SeaMonkey account.
• Multiple User Profiles: This software also lets users create and maintain multiple user profiles of one or more users.

Additional Features:

• Browser: This software comes with an inbuilt web browser to browse the internet within this software.
• Import: It allows users to import existing emails, calendars, address books, filters, etc.
• Password Manager: Use it to store and manage all your passwords from one place.

Final Thoughts:

It is another good open source Outlook alternative software through which users can send/ receive emails, schedule tasks, etc., similar to Outlook.

Zimbra

Zimbra is another free open source Outlook alternative software for Windows, macOS, and Linux. Through this software, users can easily compose emails, send emails, receive emails, manage emails, categorize emails, etc., similar to Outlook. Besides this, it also possesses the features to schedule meetings and tasks on the calendar. Let’s take a brief look at the main features of this software.

Main Features:

• Mail: It is the primary area through which users can compose emails, reply to emails, view inbox, view sent folder, manage outbox, etc. Plus, basic email search and sorting tools are also present in it.
• Calendar: Using it, users can schedule new appointments and view existing appointments along with tasks and events.
• Address Book: It allows uses to add and manage senders and their contact information so that users can quickly send emails to saved contacts.
• Tasks: With its use, users can create new tasks and events and add detailed information about them. All the scheduled tasks can be viewed on the Calendar.

Additional Features:

• Offline Mode: This mode allows users to use this software in the absence of the internet.

Final thoughts:

It is a beautifully designed open source Outlook alternative software that offers many useful email associated features that you get in Outlook.

Sylpheed

Sylpheed is another free open source Outlook alternative software for Windows, BSD, Linux, and macOS. It is a lightweight software through which users can manage emails, send emails, compose emails, manage contacts, etc., similar to Outlook. Let’s take a brief look at the primary features of this software.

Main Features:

• Email Tools Panel: This panel offers all the standard email features like inbox, drafts, trash, junk, sent mail, etc.
• Address Book: It is similar to Outlook address book through which users can manage existing contacts (phone number, email address, etc.) and add new contacts.
• Receive: This feature lets users switch between their email accounts and view emails of a specific account.
• Get All: It is another handy feature that lets users receive emails of all their accounts in one common inbox area.

Additional Features:

• Import and Export Mail Data: Through these features, users can import and export emails in EML, DBX, etc., formats.
• Delete Duplicate Messages: As its name implies, it is used to find and delete duplicate emails.

Final Thoughts:

It is another good open source Outlook alternative that offers many useful email features similar to Outlook.

Claws Mail

Claws Mail is another free open source Outlook alternative software for Windows, Ubuntu, Fedora, and Debian. Through this Outlook alternative, users can manage emails of one or more email accounts. Plus, all the essential email associated features are present in it. Let’s take a brief look at the main features of this software.

Main Features:

• Side Tools Panel: Through this panel, you can access your inbox, sent mails folder, drafts, trash, etc., features.
• Message: Through this section, users can manually choose whether they want to receive messages from a specific account or from all accounts.
• Filters: Using it, users can filter emails according to parameters like date, keywords, etc.

Additional Features:

• Offline Mode: This mode allows users to access this software and its services without access to active internet.
• Import and Export Mbox files: In this email client, users can also import and export your message and emails in the form of Mbox files.

Final Thoughts:

It is another good open source Outlook alternative software through which users can manage and send/ receive emails.