mail-abbrev-syntax-table

mail-abbrev-syntax-table is a variable defined in `mailabbrev.el'.
Its value is

nil

Documentation:
The syntax-table used for abbrev-expansion purposes.
This is not actually made the current syntax table of the buffer, but
simply controls the set of characters which may be a part of the name
of a mail alias. The value is set up, buffer-local, when first needed.