In recent builds of kde4, kmail blocks at around 90% on sending large (5-6Mb) 
messages via smtp. A dialogue pops up saying Mail not sent (Malformed address) 
and asks whether to continue or abort sending messages. However, the email IS 
sent, and since I try again, the recipient receives it multiple times. The 
cancel button won't stop the sending so have to close kmail, at which point it 
crashes (see backtrace below). This may be two different bugs, but I've been 
getting it repeatly for the last week, so wanted to report. The backtrace is 
from a build this morning of 827073.

Application: KMail (kmail), signal SIGABRT
Using host libthread_db library "/lib/libthread_db.so.1".
[Thread debugging using libthread_db enabled]
[New Thread -1209219376 (LWP 3090)]
[KCrash handler]
#6  0x00110402 in __kernel_vsyscall () 
#7  0x02506690 in raise () from /lib/libc.so.6
#8  0x02507f91 in abort () from /lib/libc.so.6
#9  0x0015bbc9 in qt_message_output (msgType=QtFatalMsg, 
    buf=0xbfd81ce0 "ASSERT: \"!transferInProgress( serNum )\" in file 
/home/kde-devel/kde/src/kdepim/kmail/messageproperty.cpp, line 161")
    at global/qglobal.cpp:2058
#10 0x0015bc2d in qFatal (msg=0x2ac518 "ASSERT: \"%s\" in file %s, line %d")
    at global/qglobal.cpp:2260
#11 0x0015c093 in qt_assert (
    assertion=0xfd5279 "!transferInProgress( serNum )", 
    file=0xfd5240 "/home/kde-devel/kde/src/kdepim/kmail/messageproperty.cpp", 
    line=161) at global/qglobal.cpp:1828
#12 0x00c8cb06 in KMail::MessageProperty::forget (msgBase=0x9546e48)
    at /home/kde-devel/kde/src/kdepim/kmail/messageproperty.cpp:161
#13 0x00cef357 in ~KMMsgBase (this=0x9546e48)
    at /home/kde-devel/kde/src/kdepim/kmail/kmmsgbase.cpp:124
#14 0x00b49bdc in ~KMMessage (this=0x9546e48)
    at /home/kde-devel/kde/src/kdepim/kmail/kmmessage.cpp:225
#15 0x00cefb5a in KMMsgList::clear (this=0x9068280, doDelete=true, 
    syncDict=false) at /home/kde-devel/kde/src/kdepim/kmail/kmmsglist.cpp:37
#16 0x00d55890 in KMFolderMaildir::close (this=0x9068230, aForced=true)
    at /home/kde-devel/kde/src/kdepim/kmail/kmfoldermaildir.cpp:259
#17 0x00c563b4 in KMFolder::close (this=0x9068488, owner=0xfea6b2 "kmkernel", 
    force=true) at /home/kde-devel/kde/src/kdepim/kmail/kmfolder.cpp:513
#18 0x00d6a666 in KMKernel::cleanup (this=0xbfd83ef0)
    at /home/kde-devel/kde/src/kdepim/kmail/kmkernel.cpp:1668
#19 0x0804b001 in main (argc=3, argv=0xbfd84074)
    at /home/kde-devel/kde/src/kdepim/kmail/main.cpp:132
#0  0x00110402 in __kernel_vsyscall ()