feedmail-queue-slug-suspect-regexp

feedmail-queue-slug-suspect-regexp is a variable defined in `feedmail.el'.
Its value is

"[^a-z0-9-]+"

Documentation:
Regular expression for characters/substrings to be replaced.
When feedmail creates a filename from a subject string, it puts hyphens
in place of strings which may cause problems in filenames. By default,
only alphanumeric and hyphen characters are kept, and all others are
converted. In non-ASCII environments, it may be more helpful to
tweak this regular expression to reflect local or personal language
conventions. Substitutions are done repeatedly until the regular expression
no longer matches to transformed string. Used by function
feedmail-tidy-up-slug and indirectly by feedmail-queue-subject-slug-maker.

You can customize this variable.

This variable was introduced, or its default value was changed, in version 24.1 of Emacs.