When comparing Mozilla Thunderbird vs Microsoft Outlook, the Slant community recommends Mozilla Thunderbird for most people. In the question“What are the best e-mail clients for macOS?” Mozilla Thunderbird is ranked 3rd while Microsoft Outlook is ranked 17th.
Ranked in these QuestionsQuestion Ranking
Pro Free (as in freedom and beer)
Pro Lightning Calendar and Address Book integration
Pro Good filtering system
Mozilla Thunderbird offers a flexible filtering system with the ability to set flags and read/unread, as well as sort/assign to new mail directories. There are also numerous plugins available to assist in the filtering.
Pro Consistent and involving a moderate learning curve
The app design of Mozilla Thunderbird has not changed significantly since its beginning, making its learning curve almost non-existent.
Pro Very reliable
Version after version, Mozilla Thunderbird works as expected.
Pro Available on Linux, OS X and Windows
Pro Large assortment of plugins available
Mozilla Thunderbird offers a huge amount of extensions to expand the usability and options of the client.
Pro Tabs for navigation
Pro Integrates with cloud storage services
Microsoft Outlook comes with built-in cloud storage browser allowing you to attach files directly from services such as Dropbox, Box, Google Drive or OneDrive to emails and directly open attached files without the need for the main cloud storage app.
Pro Good built-in calendar
The calendar includes agenda, day and three-day views.
Pro Quick swipe features
Microsoft Outlook comes with quick swipe features where users can quickly swipe the thread either from left (to schedule) or right (to delete or archive). Additionally, users can also customize the swipe actions to, for example, set swipe from left to archive or swipe from right to delete.
Pro Excellent notifications center calendar widget
Pro Good built-in contacts
In addition to showing contact information, the People section of Outlook can show all conversations you've had with a person. Moreover, if you're looking for someone that's not in your contact's list, but is in your company's or school's directory, Outlook can pull that information through integration with Global Address List (GAL).
Pro Helps prioritize email
The app will automatically attempt to figure out which emails are important to you and surface those. The priority emails will show up in your inbox in a tab called Focused, with other emails in a tab called Other. It aims to separate spam and promotional emails from the important emails.
Pro Integrates with Microsoft services
Con Development slowed to only focus on stability and security
Mozilla Thunderbird has slowed down its development of features to only focus resources on security and stability.
Con Terrible integration with macOS
Simple things - drag/dropping pictures doesn't work, for instance.
Con Outdated interface
Thunderbird's interface is very outdated and unpleasant. It feels more like a Windows XP application than like a modern MacOS one.
Con Doesn't follow security guidelines
The app stores user information and credentials on outside servers which is a violation of ActiveSync password requirement policies. These security concerns have been enough of an issue that European Parliament has banned its members from using the app out of fear that it might lead to leaking sensitive information.