Glimmer Train is a triannual publication that takes only short stories.
They accept simultaneous submissions as well as previously published pieces, if they fit within certain parameters.
There is no mention of multiple submissions but Glimmer Train breaks the year up into various contests. All are paid, some have a fee to cover the award, others are free but offer less pay.
Glimmer Train prefers online submissions but will accept snail mail.
Response time is dictated by the publication and contest timeline.