[h-e-w] vm-sort-messages author

[ed park]

in my VM 7.00 in Summary buffer, when i do M-x vm-sort-messages and
specify author as the sort key, messages by the same author get
grouped together, but the author groups are not shown in alphabetical
order.  

is there a way to get the list of messages sorted alphabetically?  i
looked in vm-sort.el and didn't find anything that helped me.

GNU Emacs 21.1.1 (i386-msvc-windows98.2222) of 2001-10-23 on SPARKYBEAR

thanks, ed