When comparing Mozilla Thunderbird vs Mailplane 3, 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 Mailplane 3 is ranked 18th.
Ranked in these QuestionsQuestion Ranking
Pro Lightning Calendar and Address Book integration
Pro Free (as in freedom and beer)
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 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 Very reliable
Version after version, Mozilla Thunderbird works as expected.
Pro Tabs for navigation
Pro Doubles as a calendar
Mailplane 3 combines Google Calendar and Gmail within a single app.
Pro Can work with mutiple Gmail accounts simultaneously
The tabbed interface included in Mailplane 3 lets users work with as many Gmail accounts simultaneously as they want.
Pro Supports many plugins
Functionality and features can be extended by using plugins.
Pro Easy to use
Mailplane 3 looks just like Gmail's web UI and even imports Gmail shortcuts. If Gmail shortcuts aren't ideal for the user, those of Mac can be used instead.
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Con Outdated interface
Thunderbird's interface is very outdated and unpleasant.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 Terrible integration with macOS
Simple things - drag/dropping pictures doesn't work, for instance.
Con Can freeze very often
Con Gmail only
Mailplane 3 is a Gmail-only client. It does not support other email providers.