The msx and msy fonts were designed by the American Mathematical Society in the very early days of TeX, for use in typesetting papers for mathematical journals. They were designed using the ‘old’ MetaFont, which wasn’t portable and is no longer available; for a long time they were only available in 300dpi versions which only imperfectly matched modern printers. The AMS has now redesigned the fonts, using the current version of MetaFont, and the new versions are called the msa and msb families.
Nevertheless, msx and msy continue to turn up. There may, of course, still be sites that haven’t got around to upgrading; but, even if everyone upgraded, there would still be the problem of old documents that specify them.
If you have a tex source that requests msx and
msy, the best technique is to edit it so that it requests
msa and msb (you only need to change the single
letter in the font names).
A partial re-implementation of the blackboard-bold part of the msy font (covering C, N, R, S and Z, only) is available in Type 1 format; if your mathematical needs only extend that far, the font could be a good choice.
If you have a DVI file that requests the fonts, there is a package of virtual fonts to map the old to the new series.
This answer last edited: 2012-03-09
This question on the Web: http://www.tex.ac.uk/cgi-bin/texfaq2html?label=msxy