Daniel,Rose,DR@example.com,http://www.example.com,1234567890
Daniel1,Rose,DR1@example.com,http://www.example.com,1234567890
Daniel2,Rose,DR2@example.com,http://example.com,1234567890
Daniel3,Rose,DR3@example.com,www.example.com,1234567890
Daniel4,Rose,DR4@example.com,1234567890,example.com

DR@example.com
http://www.example.com
DR1@example.com
http://www.example.com
DR3@example.co
www.example.com
DR4@example.com

$ sed -r 's|.*,([^,]+@[^0-9]+),.*|1|' file | tr ',' 'n'
DR@example.com
http://www.example.com
DR1@example.com
http://www.example.com
DR2@example.com
http://example.com
DR3@example.com
www.example.com
DR4@example.com