When comparing Mozilla Thunderbird vs Claws Mail, the Slant community recommends Mozilla Thunderbird for most people. In the question“What are the best e-mail clients for Windows?” Mozilla Thunderbird is ranked 1st while Claws Mail is ranked 13th.
Ranked in these QuestionsQuestion Ranking
Pro Free (as in freedom and beer)
Pro Lightning Calendar and Address Book integration
Pro Available on Linux, OS X and Windows
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 Very reliable
Version after version, Mozilla Thunderbird works as expected.
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 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 Send large files easy
Install pCloud plugin for Thunderbird and your files (upto 20 GB free storage included) will be received as download links
Pro Low resource client
Claws Mail is a low resource e-mail client that is often default in low resource Linux distributions.
Pro Has many plugins for extra functionality
Pro Clean interface with 5 layout variants
Pro Good support for Google's services
Pro Saves emails in uncompressed readable format
Allows one to read archived emails with a text editor.
Pro Has very strong filters
The filters a much stronger than in thunderbird
Pro Traditional user interface
Pro Has many themes
Con Terrible integration with macOS
Simple things - drag/dropping pictures doesn't work, for instance.
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 Subject lines can (temporarily) disappear from the list
This is sporadic behavior.
Con Serious bugs
Clicking on a subject line can bring up the wrong email.
Con Outdated interface
Thunderbird's interface is very outdated and unpleasant.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 saves password in plain format
Con Interface looks old and setup is not easy
The icons as well as the rest of the interface look like an application from the early 90's, with this there is also no easy setup options built in like the more modern e-mail clients.
Con Also supported on Windows
This makes switching the platform easier.
Con Saves emails in uncompressed format
This takes more space on the HDD.