A special format of PostScript files is encapsulated PostScript or eps. Encapsulated PostScript was designed to allow graphic material from one program to be transferred and used in a document produced by another program. This goes beyond the usual role of PostScript files as an intermediary between programs and printers. A number of word processors and graphics programs such as Frame Maker, Corel Draw, and LaTeX are able to import encapsulated PostScript drawing from such programs as Gnuplot.
If your application says it imports encapsulated PostScript, it actually does require encapsulated PostScript; straight PostScript will not work. You can identify encapsulated PostScript by the first lines of the document. They should look something like this:
%!PS-Adobe-2.0 EPSF-1.2 %%DocumentFonts: Times-Bold %%Pages: 1 %%BoundingBox: 65 493 550 786 %%EndComments
The key is the EPSF label in the first line. The rest of the file varies depending on the application that wrote it.