When comparing Mozilla Thunderbird vs Kontact, the Slant community recommends Mozilla Thunderbird for most people. In the question“What are the best native e-mail clients for Linux?” Mozilla Thunderbird is ranked 1st while Kontact is ranked 6th.
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 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 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 Integrated calendaring
The integrated calendaring support means that incoming invitations can be accepted with a click and they get put into your calendar automatically.
Pro Multi-account, multi-identity
Supports both multiple accounts from different servers / services simultaneously (both inbound and sending) as well as multiple identities. Incoming accounts have a default identity and it switches automatically to the correct identity depending on the mail folder you are in.
Fully supports PGP and S-MIME with built-in certificate management. Encrypt, sign and verify emails easily and securely.
Pro Contacts, Todos, Notes, Journals, Feeds ....
There are numerous components that come with Kontact that augment the mail experience including contact management, todo lists, note takers and an RSS feed reader, among others.
Pro Supports multiple groupware servers and services
Besides being able to connect to any IMAP, POP3 and SMTP server, you can also connect your Google and Facebook accounts and access Kolab and Tine servers natively.
Pro Continuous, active development
Kontact has been actively developed for over a decade, with components such as the mail and calender going back even further. Development continues to this day with an active and responsive open source community made up of both volunteers and paid developers behind it.
Pro Solid offline IMAP
IMAP support is a strong point for Kontact, with offline mail and sync being transparent and automatic. Read and create mails on the go and everything syncs quickly and reliably when network connectivity is available.
Pro Built-in search
Searching for emails is simple with the search box in the main window which can scan through email bodies, email flags, recipients, etc. Lightening fast in recent versions.
Pro Spam, scam and adblock features
Supports spam filtering, scam detection and adblock for HTML mails.
Pro Keyboard friendly
Can be driven almost entirely from the keyboard. Moving an email, for instance, is a simple matter of hitting 'm' and then typing to filter through the list of folders that appears.
Pro Plain text and HTML mail editing
Provides support for rich-text (HTML) mail editing, but kindly defaults to plain text. Also supports viewing HTML emails with several security features built-in.
Works on Linux/BSD (all desktop environments and window managers), Windows and Mac.
Has flexible and powerful options, from "traditional" conversation-style threading to organizing by date, by senders and receivers, .... paired with "keep replies in same folder" it is easy to track conversations over time.
Supports client and server-side filtering of mails by subject, recipients, mailing list, body text, etc.
Pro Very flexible user interface
You can make the Kontact UI look and function how you want. You can re-arrange the main interface, as well as make the list of mails show or hide almost anything you could need.
Pro Professional support
For enterprise deployments, having commercial support can be a big plus. Companies such as Kolab Systems provide professional support and consulting services for Kontact.
Pro Integration with kde plasma
Based on qt, and part of plasma suite, it integrates well with other KDE apps like kwallet, calendar, etc.
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 Terrible integration with macOS
Simple things - drag/dropping pictures doesn't work, for instance.