There are a few email options in Lightroom, what option are you using? One of them is to select Apple Mail in the list, where it should just be relayed through the app.
The other is to setup your POP3 and SMTP settings from your server directly.
You can also use Mail as an Export Action in Export.
I just figured out how to answer you directly. As I wrote a few minutes ago, I was aware that I could email images through Apple Mail, but I hardly use that server. I was able to add one of my yahoo addresses, authenticating it, and now can send images through yahoo. I researched the issue further with gmail, and apparently, one has to have a 2 step verification process, which I started to do, but then stopped, not knowing how this would effect my use of gmail when sending emails without images.
I also don't have a clue what POP3 is or SMTP.