I downloaded e-Newsletter 2.6.1. But I failed to install it. If I install 2.6.1 manullay after I delete 2.5.9 version, I'm afraid to lose all my test data such as test group, test newsletter, and .po and .mo file for Korean translation. (If you want translation file, I will send it to you.)
WPDEV plugin is read like "most plugins and themes are able to be auto-updated depending on where they are installed".
Would you tell me how to upgrade the current version into the newest version.