I'm surprised the recent KMail problem has not been solved.
The symptoms in my case, in brief, are
1. I am using KMail on my laptop with dovecot/IMAP
to read mail collected on my desktop;
2. KMail crashes when reading, or even accessing, certain messages.
These are nearly all, if not all, mailing list digests.
I guess the property they have in common might be
that they have a large number of references to other messages or URLs.
I submitted a bugzilla, which bizarrely to me
was declared a duplicate of a bugzilla over a year old
and which appeared to deal with another symptom,
KMail crashing when it starts.
There are a large number of duplicates listed,
nearly all very recent.
It seems to me fairly obvious that the problem has arisen recently,
and is due to a recent change in KMail (or possibly dovecot).
e-mail: gayleard /at/ eircom.net
tel: +353-86-2336090, +353-1-2842366
s-mail: School of Mathematics, Trinity College, Dublin 2, Ireland