Help on e-mailing from lightroom
As said: LR wants a mail-client. If you don't want that (you're happy with your g-mail as I hear it) you can better EXPORT from LR, remember where you put the picture(s) and send them as you are used to.
All in my humble opionion of course!
If I seem to talk nonsense or you can't understand me, it's probably my English