Issue: I got some Clients using OutLook or Web based Mail reader disclaimed for garbled attach filename (Japanese or UTF8 encoded filename) on Pega email notice. It came from mime encoding issue.
Root Cause: On some infrustructure, could not detect the filename charactor code properly. mistook unicode string as ascii characters. As the result it set unicode binary onto the filename= value of Content-Disposition: parameter.
The issue happens because Outlook cannot correctly read Japanese characters in email attachment filenames, which is caused by incorrect MIME encoding settings in the system. To fix this, you need to configure the application server to properly handle UTF-8 encoding for filenames. Set the JVM parameter -Dfile.encoding=utf-8 so the system uses UTF-8 as the default character encoding. Also enable proper MIME filename encoding by adding -Dmail.mime.encodefilename=true. After applying these settings, restart the server so the changes take effect. This ensures attachment filenames are correctly encoded and displayed in Outlook without garbling.