Sometimes, you will encounter a pop-up message “Provider cannot be found. It may not be properly installed” when you import .xlsx file (Excel 2007, or Excel 2010) into 1and1Mail Address Book or Multi Account Manager.
Your OS does not have the library to decode .xslx file.
1. Install the new Microsoft library (Data Connectivity Components) from http://www.microsoft.com/download/en/details.aspx?displaylang=en&id=23734
2. Save your .xlsx file as .xls file (Excel 97 – 2003 format) and then import the .xls file.
3. Save your .xlsx file as .csv file, and then import the .csv file.