Selenium Webdriver - Not able to enter text in a textbox through sendKeys()

Selenium Webdriver - Not able to enter text in a textbox through sendKeys()

Not able to enter text in a textbox through sendKeys(). It is a email id
textbox. Following is the entire code
<div class="line split_column"> <div class="unit control size1of1">
<div id="contacts_selector_list" class="option_selector" style="display:
block; position: relative; z-index: 3;">
<div class="input full_width_input selector_input_box">
<div class="drop_down_container mtn"
style="display: none;"> </div> </div> </div>