mh-default-folder-must-exist-flag

mh-default-folder-must-exist-flag is a variable defined in `mh-e.el'.
Its value is

t

Documentation:
*Non-nil means guessed folder name must exist to be used.

If the derived folder does not exist, and this option is on, then
the last folder name used is suggested. This is useful if you get
mail from various people for whom you have an alias, but file
them all in the same project folder.

See `mh-prompt-for-refile-folder' and `mh-folder-from-address'
for more information.

You can customize this variable.

This variable was introduced, or its default value was changed, in version 7.2 of the MH-E package that is part of Emacs 22.1.