Command + Shift + M (Mac) | Control + Shift + M displays the options to Email Photos in Lightroom.
If you are using an email program (such as Outlook), you can simply choose it using the “From” list. If however, you are using a web based email, use the “From” option to choose “Go To Email Account Manager”. Click the Add (+) icon in the lower left and, if you’re using one of the 4 programs listed (AOL mail, gmail, Windows Live Hotmail or Yahoo! mail), select them from the list. If you’re using another program, then you will need to get the necessary information from your email provider. Note the default email preset (for size and quality) also include copyright and contact information, but you can create your own preset by selecting Create New Preset from the Preset list in the lower left.