Dear Maintainer,

After upgrading my system to versions 4:26.04.3-7 of the messagelib
libraries, KMail/Kontact exits when ever I close the message composer.
First I observed this when sending a message, but it actually happens
even after
  - start kmail
  - click "New Message"
  - close the new message window
kmail then closes completely, but no crash handler is opened

when starting kmail from the commandline the last output lines are

```
free(): invalid next size (normal)
*** KMail got signal 6 (Exiting)
*** Dead letters dumped.
Alarm clock                kmail
```

Based on this observations I downgraded all the binaries from
messagelib to 4:26.04.3-2. And this fixed the problem.

(so I can not guarantee that the affected binary package is really
messagecomposer6 but this is the most likely culprit.)

Thanks for your work!

Nicola