Email notification channel - "Include image" stopped work after switch to HTTPS

After switching grafana to HTTPS mode, “Include image” in mail nottification stopped work. Grafana version was v7.0.3 , yesterday I updated to v7.3.6 to see difference (same behavior).

To debug it, I open the source code of the mail, in good mail (when using HTTP), in table class (with image) I can see line with “img src=”

Summary

img src=“cid:rjKY40ak3kFdV9Y4GOLg.png” alt=“Alerting Panel” style=“outline: none !important; text-decoration: none !important; -ms-interpolation-mode: bicubic; width: auto; clear: both; display: block; border: 0;” align=“left”

Now, the class is still there, but whole line with “img src =” is missing.
How to fix it?

Hi,
I have the same issue. After switching to HTTPS images in e-mail alerts are not working.
Is there anything in config file that needs to be changed in order to make it work?