It could be a .pdf file format. If so you would need to have installed Adobe Reader which is available from here: http://get.adobe.com/uk/reader/?promoid=JZEFU You could also try saving the attachment and save with a name of of your choice and include the name extension of .PDF e.g. 'Myfilename.PDF'. Then try opening that file from the location where you...
You could also try saving the attachment and save with a name of of your choice and include the name extension of .PDF e.g. 'Myfilename.PDF'. Then try opening that file from the location where you have save it to.