Alternatives to KMail
KDE's email client with IMAP, filtering and OpenPGP support. The listings below can replace it for an important use case. Each note says what changes if you switch.
The original
KMail
KDE's email client with IMAP, filtering and OpenPGP support.
Replacements
Listings that take over the same core job as KMail.
Thunderbird
Mozilla’s desktop mail client, with calendar, contacts and a unified inbox, funded by donations rather than ads.
Thunderbird is cross-platform with calendar, contacts and built-in OpenPGP in one application, without relying on Akonadi or the Kontact suite.
Evolution
GNOME's mail, calendar, contacts and tasks suite, and the usual answer for Exchange on Linux.
Evolution is GNOME's mail, calendar, contacts and tasks suite with an Exchange Web Services plugin, and is heavier and slower to start.
Betterbird
A Thunderbird fork that ships extra fixes and features, and can run side by side on the same profile.
Betterbird is a Thunderbird fork with extra fixes on Windows, macOS and Linux, maintained by a small volunteer project.
Claws Mail
A fast, keyboard-driven email client that loads a hundred thousand message folder without thinking about it.
Claws Mail is a fast keyboard-driven client with a PGP plugin and deep filtering, handling huge folders, but has only a vCalendar plugin.
Geary
GNOME email client built around conversation threads.
Geary is a minimal GNOME client built around conversations with fast search, but has no built-in encryption, rules engine or calendar.
Mailspring
A desktop mail client with a unified inbox, snooze and send later, whose paid tier adds read receipts.
Mailspring offers a modern unified inbox with snooze and templates on Linux, Windows and macOS, but has no built-in calendar or listed encryption.
Also worth comparing
These listings name KMail as their own alternative, so the relationship runs both ways.
Balsa
A lightweight GTK email client for the GNOME desktop.
KMail is KDE's client with integrated OpenPGP and S/MIME, but it depends on the Akonadi storage service and fits the KDE desktop better.
Similar software
Related functionality, not a direct replacement.
Proton Mail Bridge
Local gateway that lets standard mail clients read a Proton Mail account.
isync
Fast IMAP to Maildir mirroring, usually invoked as mbsync.
NeoMutt
A fork of Mutt that gathered decades of scattered patches into one maintained terminal mail client.
notmuch
A fast, tag-based email indexing and search system used from a terminal or text editor.
