After adding a new account and applying the changes kmail segfaults. 
Since then I am unable to start kmail at all (eg to remove the account again). It immediately segfaults.
Removing the account from the akonadi console does not fix this.

$ gdb kmail
GNU gdb (Ubuntu 7.10-1ubuntu2) 7.10
Copyright (C) 2015 Free Software Foundation, Inc.
(...)
Reading symbols from kmail...Reading symbols from /usr/lib/debug/.build-id/59/cf7345c7220ec736df6bedf637f89a6ceeb5ca.debug...done.
(gdb) run
Starting program: /usr/bin/kmail 
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
[New Thread 0x7fffcfd47700 (LWP 1270)]
log_kontactinterface: kontact not running -- start standalone application
log_kmail: 
log_kmail: Delaying instance creation.
log_kmail: Starting up...
"KMail Kernel ETM"
()
connectToServer "/tmp/akonadi-monster.BrlSKy/akonadiserver.socket"
""
connectToServer "/tmp/akonadi-monster.BrlSKy/akonadiserver.socket"
"/subscriber/kmail2_1263_ADYKoN"
connectToServer "/tmp/akonadi-monster.BrlSKy/akonadiserver.socket"
log_mailtransport: Have SMTP, Sendmail, and 0 Akonadi types.
log_mailtransport: "724185408"
log_mailtransport: type 0
log_mailtransport: "1157345828"
log_mailtransport: type 0
log_mailtransport: "2073349993"
log_mailtransport: type 0
log_mailtransport: "403360698"
log_mailtransport: type 0
log_mailtransport: "1225311289"
log_mailtransport: type 0
log_mailtransport: "1143571751"
log_mailtransport: type 0
log_mailtransport: 
Pass a valid window to KWallet::Wallet::openWallet().
log_kmail: 
log_kmail: KMail init with akonadi server state: 2
log_mailcommon: Initialized and looking for specialcollection folders.
"/subscriber/kmail2_1263_5pQc97"
connectToServer "/tmp/akonadi-monster.BrlSKy/akonadiserver.socket"
log_kmail: Opening autosave file: "/home/monster/.local/share/kmail2/autosave/{21c0ea52-9207-4820-b694-02c19f6128ba}"
log_messagecomposer: initalising autosave
Hspell: can't open /usr/share/hspell/hebrew.wgz.sizes.
HSpellDict::HSpellDict: Init failed
"contactsCompletionSession"
connectToServer "/tmp/akonadi-monster.BrlSKy/akonadiserver.socket"
[New Thread 0x7fffc584d700 (LWP 1279)]
log_kmail: 
log_kmail: "new-added-account@my-domain.xyz"

Program received signal SIGSEGV, Segmentation fault.
QAction::setEnabled (this=0x0, b=b@entry=false) at kernel/qaction.cpp:1020
1020    kernel/qaction.cpp: Datei oder Verzeichnis nicht gefunden.
(gdb) backtrace
#0  QAction::setEnabled (this=0x0, b=b@entry=false) at kernel/qaction.cpp:1020
#1  0x00007ffff78bedd9 in KMComposeWin::slotEditorTextChanged (this=0x927940) at ../../kmail/editor/kmcomposewin.cpp:535
#2  0x00007ffff7904c51 in KMComposeWin::qt_static_metacall (_o=_o@entry=0x927940, _c=_c@entry=QMetaObject::InvokeMetaMethod, _id=_id@entry=33, _a=_a@entry=0x7fffffffc910) at moc_kmcomposewin.cpp:484
#3  0x00007ffff600a8ea in QMetaObject::activate (sender=0x1344f80, signalOffset=<optimised out>, local_signal_index=local_signal_index@entry=0, argv=argv@entry=0x0) at kernel/qobject.cpp:3713
#4  0x00007ffff600b0e7 in QMetaObject::activate (sender=<optimised out>, m=m@entry=0x7ffff6ddd640 <QTextEdit::staticMetaObject>, local_signal_index=local_signal_index@entry=0, argv=argv@entry=0x0)
    at kernel/qobject.cpp:3578
#5  0x00007ffff6a7e300 in QTextEdit::textChanged (this=<optimised out>) at .moc/moc_qtextedit.cpp:524
#6  0x00007ffff6a84025 in QTextEdit::qt_static_metacall (_o=_o@entry=0x1344f80, _c=_c@entry=QMetaObject::InvokeMetaMethod, _id=_id@entry=0, _a=_a@entry=0x7fffffffca80) at .moc/moc_qtextedit.cpp:318
#7  0x00007ffff600a8ea in QMetaObject::activate (sender=0x1243230, signalOffset=<optimised out>, local_signal_index=local_signal_index@entry=0, argv=argv@entry=0x0) at kernel/qobject.cpp:3713
#8  0x00007ffff600b0e7 in QMetaObject::activate (sender=<optimised out>, m=m@entry=0x7ffff6ddf1e0 <QWidgetTextControl::staticMetaObject>, local_signal_index=local_signal_index@entry=0, argv=argv@entry=0x0)
    at kernel/qobject.cpp:3578
#9  0x00007ffff6a9bb60 in QWidgetTextControl::textChanged (this=<optimised out>) at .moc/moc_qwidgettextcontrol_p.cpp:481
#10 0x00007ffff6aa4fbd in QWidgetTextControl::qt_static_metacall (_o=_o@entry=0x1243230, _c=_c@entry=QMetaObject::InvokeMetaMethod, _id=_id@entry=0, _a=_a@entry=0x7fffffffcc00)
    at .moc/moc_qwidgettextcontrol_p.cpp:254
#11 0x00007ffff6aaa0a0 in QWidgetTextControl::qt_metacall (this=0x1243230, _c=QMetaObject::InvokeMetaMethod, _id=0, _a=0x7fffffffcc00) at .moc/moc_qwidgettextcontrol_p.cpp:451
#12 0x00007ffff600aaa0 in QMetaObject::activate (sender=sender@entry=0x12433b0, signalOffset=<optimised out>, local_signal_index=local_signal_index@entry=1, argv=argv@entry=0x0) at kernel/qobject.cpp:3728
#13 0x00007ffff600b0e7 in QMetaObject::activate (sender=sender@entry=0x12433b0, m=m@entry=0x7ffff6767e00 <QTextDocument::staticMetaObject>, local_signal_index=local_signal_index@entry=1, argv=argv@entry=0x0)
    at kernel/qobject.cpp:3578
#14 0x00007ffff669f0b3 in QTextDocument::contentsChanged (this=this@entry=0x12433b0) at .moc/moc_qtextdocument.cpp:378
#15 0x00007ffff642ab15 in QTextDocumentPrivate::contentsChanged (this=0x1149930) at text/qtextdocument_p.cpp:1646
#16 QTextDocumentPrivate::finishEdit (this=0x1149930) at text/qtextdocument_p.cpp:1238
#17 0x00007ffff642e7ed in QTextDocumentPrivate::endEditBlock (this=<optimised out>) at text/qtextdocument_p.cpp:1193
#18 0x00007ffff646f82d in QSyntaxHighlighterPrivate::rehighlight (operation=QTextCursor::End, cursor=..., this=0x12a1500) at text/qsyntaxhighlighter.cpp:69
#19 QSyntaxHighlighter::rehighlight (this=<optimised out>) at text/qsyntaxhighlighter.cpp:368
#20 0x00007ffff739138d in PimCommon::RichTextEditor::setSpellCheckingLanguage (this=0x1344f80, _language=...) at ../../pimcommon/texteditor/richtexteditor/richtexteditor.cpp:616
#21 0x00007ffff78bcbd3 in KMComposeWin::slotSpellCheckingLanguage (this=0x927940, language=...) at ../../kmail/editor/kmcomposewin.cpp:523
#22 0x00007ffff600a777 in QtPrivate::QSlotObjectBase::call (a=0x7fffffffcea0, r=0x927940, this=<optimised out>) at ../../include/QtCore/../../src/corelib/kernel/qobject_impl.h:124
#23 QMetaObject::activate (sender=0x915580, signalOffset=<optimised out>, local_signal_index=<optimised out>, argv=<optimised out>) at kernel/qobject.cpp:3698
#24 0x00007fffef394b02 in Sonnet::DictionaryComboBox::dictionaryChanged(QString const&) () from /usr/lib/x86_64-linux-gnu/libKF5SonnetUi.so.5
#25 0x00007fffef394bbe in ?? () from /usr/lib/x86_64-linux-gnu/libKF5SonnetUi.so.5
#26 0x00007fffef394e8e in Sonnet::DictionaryComboBox::setCurrentByDictionaryName(QString const&) () from /usr/lib/x86_64-linux-gnu/libKF5SonnetUi.so.5
#27 0x00007ffff78c5953 in KMComposeWin::readConfig (this=this@entry=0x927940, reload=reload@entry=false) at ../../kmail/editor/kmcomposewin.cpp:650
#28 0x00007ffff78d62a3 in KMComposeWin::KMComposeWin (this=this@entry=0x927940, aMsg=..., lastSignState=lastSignState@entry=false, lastEncryptState=lastEncryptState@entry=false, 
    context=context@entry=KMail::Composer::NoTemplate, id=id@entry=0, textSelection=..., customTemplate=..., __in_chrg=<optimised out>, __vtt_parm=<optimised out>) at ../../kmail/editor/kmcomposewin.cpp:458
#29 0x00007ffff78d6d21 in KMComposeWin::create (msg=..., lastSignState=lastSignState@entry=false, lastEncryptState=lastEncryptState@entry=false, context=context@entry=KMail::Composer::NoTemplate, 
    identity=identity@entry=0, textSelection=..., customTemplate=...) at ../../kmail/editor/kmcomposewin.cpp:216
#30 0x00007ffff78d6d5c in KMail::makeComposer (msg=..., lastSignState=lastSignState@entry=false, lastEncryptState=lastEncryptState@entry=false, context=context@entry=KMail::Composer::NoTemplate, 
    identity=identity@entry=0, textSelection=..., customTemplate=...) at ../../kmail/editor/kmcomposewin.cpp:209
#31 0x00007ffff77d7de0 in KMKernel::recoverDeadLetters (this=this@entry=0x7fffffffe1f0) at ../../kmail/kmkernel.cpp:1240
#32 0x0000000000404233 in main (argc=1, argv=0x7fffffffe408) at ../../kmail/main.cpp:152
(gdb) 


new-added-account@my-domain.xyz is the account i'v just added (SMTP and IMAP)

Reproducible: Always