Automatic e-mail sending system through Outlook using Macro

This is because your are utilizing early binding for you outlook variables without setting the reference to outlook in the excel file.

See https://support.microsoft.com/en-us/kb/245115 and http://excelmatters.com/2013/09/23/v...-late-binding/ for discussion on late vs early binding for automation, and why late binding is recommended in multi version environments.