In Mail.app are images for a gmail account pulled from google image proxy servers or original servers? When using Mail.app to access a gmail account, will images get pulled from the google image proxy servers or from the original servers? 

From https://support.google.com/mail/answer/145919?hl=en


  How Gmail makes images safe
  Some senders try to use externally linked images in harmful ways, but Gmail takes action to ensure that images are loaded safely. Gmail serves all images through Google’s image proxy servers and transcodes them before delivery to protect you in the following ways:
  
  Senders can’t use image loading to get information like your IP address or location.
  Senders can’t set or read cookies in your browser.
  Gmail checks your images for known viruses or malware.
  In some cases, senders may be able to know whether an individual has opened a message with unique image links. As always, Gmail scans every message for suspicious content and if Gmail considers a sender or message potentially suspicious, images won’t be displayed and you’ll be asked whether you want to see the images.
Apple's Mail.app fetches email over IMAP. Gmail does not replace any image URLs when email is accessed through IMAP, therefore images come directly from the original source.

You can verify that by reviewing the raw source of the email in your IMAP client (e.g. Mail.app). Select View > Message > Raw Source from the menu. Alternatively, use the keyboard shortcut Option-Command-U.