With the latest update to Lightroom CC, 2015.1 (I'm not sure if this has changed in Lightroom 6.1) Adobe has changed the way Lightroom handles emailing images. In the past when you choose the option to email some images by using the "Email Photo(s)..." option from the menu, Lightroom would open a dialog which let you see the images you were going to email, and allow you to enter addresses if you wanted to. It would then pass the photos on to your email client which would handle the actual emailing of the images. In the latest version Lightroom now seems to include its own email sending software, and now requires you to enter the details of your mail server, and compose and send the email directly inside of Lightroom.