Question: How can you make Communicator encode attachments in base64 binary encoding? Answer: You can add the following line to the prefs.js file to force Communicator to use base64 encoding with mail and news attachments. user_pref("mail.file_attach_binary", true); It's a new preference available beginning in version 4.5. Adding this line may solve some attachment file corruption problems. Remove the preference to return to the default, where Communicator guesses at quoted-printable vs. base64 based on the file contents. To edit your prefs.js file: 1.Close Communicator. 2.Before you edit the prefs.js file, make a backup copy of it. To do that, right-click it and choose Copy from the popup menu. Give the copy a name like prefs.bak. 3.Open the prefs.js file in Notepad: a.Click the Windows Start button and choose Programs, Accessories, and then Notepad. b.From the Notepad File menu, select Open. c.Browse to your Communicator user profile folder. Next to "Files of type" click the drop-down menu and choose "All Files (*.*)"; otherwise you'll only see .txt files in that folder. d.Click once on the prefs.js file and click Open. You should now see the contents of the prefs.js file displayed in Notepad. 4.Type: user_pref("mail.file_attach_binary", true); Make sure that all the text you type is in the same case as it appears above. 5.Go to the File menu and select Save. 6.From the File menu, select Exit to close Notepad. Answer: You can add the following line to the prefs.js file to force Communicator to use base64 encoding with mail and news attachments. user_pref("mail.file_attach_binary", true); It's a new preference available beginning in version 4.5. Adding this line may solve some attachment file corruption problems. Remove the preference to return to the default, where Communicator guesses at quoted-printable vs. base64 based on the file contents. To edit your prefs.js file: 1.Close Communicator. 2.Before you edit the prefs.js file, make a backup copy of it. To do that, right-click it and choose Copy from the popup menu. Give the copy a name like prefs.bak. 3.Open the prefs.js file in Notepad: a.Click the Windows Start button and choose Programs, Accessories, and then Notepad. b.From the Notepad File menu, select Open. c.Browse to your Communicator user profile folder. Next to "Files of type" click the drop-down menu and choose "All Files (*.*)"; otherwise you'll only see .txt files in that folder. d.Click once on the prefs.js file and click Open. You should now see the contents of the prefs.js file displayed in Notepad. 4.Type: user_pref("mail.file_attach_binary", true); Make sure that all the text you type is in the same case as it appears above. 5.Go to the File menu and select Save. 6.From the File menu, select Exit to close Notepad.