Email SIngle or Multiple Full-Resolution Photos From the iPhone – You'll need to Copy and Paste the photo into the Mail program to send the full-sized, original version of the image.
To perform the operation for multiple images, Ryan has the procedure in the comments:
… next to the Share button at the bottom of the Select Photos screen, there is also a Copy button. This allows you to copy as many pictures as you’d like which you can then paste in an email and send them at 2048×1536.