When I got rid of OpenOffice and installed LibreOffice, I ran into a problem. Attachments in the MSWord or MSExcel formats (.doc and .xls files) would not open when clicked on. Thunderbird would properly open attachments in the Open Office/LibreOffice file formats, but not the Microsoft format files. In checking the file associations, I found they were all correct. MS Word files were set to open with LibreOffice Writer, and the MS Excel files were set to open with LibreOffice Calc, but they did not work. HERE IS THE SOLUTION... 1) Reset the file associations for the Microsoft format files to "Always Ask." 2) Open an email with an MS Word attachment. (a doc file) 3) Click to open the attachment. 4) Thunderbird will ask you "What should Thunderbird do with this file?" 5) Tell it to use LibreOffice Writer 6) Check the box to "Do this automatically for files like this from now on." 7) Do the same with an Excel spreadsheet file. DONE. Microsoft format files will now open properly from Thunderbird in LibreOffice.