Steinar Bang <sb@metis.no> writes:
   Occasionally I get the message "Can't move article!", when I attempt
   to move an article from one nnml group to another, using
        B m

   in the summary buffer. Other articles can be moved without problem (on
   a set of process marked articles, some are moved, others are left
   untouched).
   
   Yair Friedman <yfriedma@JohnBryce.Co.Il> suggests:
   What is the value of nnmail-keep-last-article? If it is t and the
   article is last in the group, you can't move it.
   
   To this, Steinar Bang <sb@metis.no> adds:
   You should add that nnmail-keep-last-article can be set specifically
   for single groups, in the Group Parameters of that group. (ie. if the
   global setting is t, you can set it to nil for one particular group,
   by putting
        (nnmail-keep-last-article nil)

   in group parameters
        G p

   in the *Group* buffer. (It may work the other way around as well, but
   I haven't actually _verified_ that setting it to t in Group
   Parameters, will make it leave the last article, when expiring))