Unexpected interpreter error -21. The checking performed by ghostscript is strict. A postscript printer will ignore some errors in an attempt to output the file. However, it is worth making your postscript file work without any errors so that it can be viewed on screen. File Corrupted by Email Don't send raw postscript files through email.
Mail programs can corrupt raw postscript files by introducing spurious line-breaks.
N.B. trailing characters may not be detected by checking with ghostscript, since they follow the end of the postscript. Leading garbage, such as mail headers, can also cause problems. Out of Range Coordinates Buggy graphics programs occasionally output spurious large coordinates which overflow the normal range of integers. Check for more recent and hopefully bugfixed versions of your graphics software. The offending coordinate can usually be replaced by zero without affecting the final output, because it is usually followed by a valid moveto command which cancels its effect.