Personally I don't use the Built In emailing feature. I do use the Email Photo feature in LR but with that I use the Email program that is installed on my system. That way I have a recorded of what images I have email and to who. Not sure LR saves that data and if it is accessible within LR.
Have you tried using the email program you use on a daily basis? In the Email Photo dialog window just select your current email program. Mine is MozillaThunderbird.