Version:           4.8 (using Devel) 
OS:                Linux

When I try to open INBOX on an IMAP account KMail hangs. Strace
shows that it always hangs in a futex call.

I think it is caused by a race condition because when I run KMail
in strace, I'm unable to reproduce the issue (it's obviously running slower).
It only happens when I run KMail on it's own, strace -p `pidof kmail` of 
the frozen KMail then shows

$ strace -p `pidof kmail`
Process 5672 attached - interrupt to quit
futex(0x7f546fcac8a0, FUTEX_WAIT_PRIVATE, 2, NULL


It happens only with INBOX, other folders can be opened and I can switch
between emails. It freezes sometimes when I switch between emails to 
quickly (but only sometimes, does not seem to be regular).

Let me know if you need any more information.

Reproducible: Sometimes

Steps to Reproduce:
1) run KMail with IMAP account
2) open INBOX
3) KMail freezes
4) strace -p `pidof kmail` will show it hangs in futex()

Actual Results:  
KMail freezes

Expected Results:  
KMail should not freeze :)