mh-alias-flash-on-comma

mh-alias-flash-on-comma is a variable defined in `mh-e.el'.
Its value is

t

Documentation:
*Specify whether to flash address or warn on translation.

This option controls the behavior when a [comma] is pressed while
entering aliases or addresses. The default setting flashes the
address associated with an address in the minibuffer briefly, but
does not display a warning if the alias is not found.

You can customize this variable.

This variable was introduced, or its default value was changed, in version 7.1 of the MH-E package that is part of Emacs 22.1.