As of Sep 3, 2019, version: 6.0.190811, you can Choose to be asked before external images are displayed automatically.
To enable this for new incoming messages, go to Settings > specific account > Images and select Ask before displaying external images.
Gmail App - Account Settings - General
Try to enable less secure app access in https://myaccount.google.com
(If you have several gmail account, check if this page is connected to the right account).
In my case it was OFF, I could download the mail, but could not send them.
I had the same problem, and finally found this discussion. After trying some of the other older setting recommendations I had found elsewhere, I found this resolution, so opened gmail within Google Chrome browser, and the links work. 'Too bad if the app no longer works on my iPad! First I had to dump the ebay app, and now gmail too...?
I found a method that partially answers my question of where all the outbound traffic is going. In looking at Little Snitch again I realized that I could get aggregate data for traffic to some sites that the program communicates with. This data covers about half of all the outbound data the program has ever sent. I put this info into a spreadsheet and ...