Recurring KMail issue in Testing.

[Andy G Wood <agw@bas.ac.uk>]

In recent weeks I have been getting a seemingly random issue with KMail v5.9.3 
in Testing.  Now and again on sending an email I get the following notification 
pop-up:

Email sending failed.
Failed to store result in item. Only resources can modify remote identifiers.

The email sending does not fail, but the local administration of the fact that 
an email has been sent does fail (the outgoing email is put un-read in sent-
mail with an icon of an envelope superimposed with a small arrow, bottom 
right)

No akonadi error seems to be logged (which I am guessing is where the problem 
is coming from).  I don't really know how to debug this further?

Andy.