Akonadi ABI breaks every single day between packages from different repos. Please keep ABI stable or package everything under the same version number. Having KMail be unlauncable 6 out of 7 days of the week in "stable" KDE Neon is not professional. Feel free to redirect the bug to a more correct place if it is KDE Neon that are not following the correct procedures.
All KDEPIM packages must be installed from the same version; there is no ABI compatibility guarantee yet. For neon, this means all KDEPIM packages need to be recompiled (in correct dependency order) and released together. Current list of KDEPIM packages: akonadi akonadi-calendar akonadi-calendar-tools akonadi-contacts akonadi-import-wizard akonadi-mime akonadi-notes akonadi-search akonadiconsole akregator blogilo calendarsupport eventviews grantlee-editor grantleetheme incidenceeditor kaddressbook kalarm kalarmcal kblog kcalcore kcalutils kcontacts kdav kdepim-addons kdepim-apps-libs kdepim-runtime kholidays kidentitymanagement kimap kldap kleopatra kmail kmail-account-wizard kmailtransport kmbox kmime knotes kontact kontactinterface korganizer kpimtextedit ktnef libgravatar libkdepim libkleo libksieve mailcommon mailimporter mbox-importer messagelib pim-data-exporter pim-sieve-editor pimcommon syndication
Note that stable Neon is Developer Edition Stable Branches which means branches for bugfix releases, it doesn't necessarily mean it's stable to use as a developer edition is for developers to test from. It's badly named and I'd like to find another name.
I think all the packages probably are all recompiled on the same date (though maybe not in the right order), what is certainly missing are dependencies on exact versions between all of them so they can only migrate into the repo and be upgraded together. Some packages are specific-version tied, but not all.
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This bug has been in NEEDSINFO status with no change for at least 30 days. The bug is now closed as RESOLVED > WORKSFORME due to lack of needed information. For more information about our bug triaging procedures please read the wiki located here: https://community.kde.org/Guidelines_and_HOWTOs/Bug_triaging Thank you for helping us make KDE software even better for everyone!