Hi @eragon
I tried this numerous times without success. Copied all the contents from here to mytheme/theme/lms/templates/ace_common/edx_ace/common/base_body.html, edited lines 63-65
as
<td width="70">
<a href="https://mysite.com"><img
src="https://mysite.com/logo.png"
height="30" alt="{% filter force_escape %}{% blocktrans %}Go to {{ platform_name }} Home Page{% endblocktrans %}{% endfilter %}"/>
</a>
</td>
and rendered it. But it encountered an error
TemplateSyntaxError: Encountered unknown tag ‘load’.
So I put base_body.html contents between {% raw %} and {% endraw %} tags. Though it rendered without errors, Activation e-mail still looks the same after building images and restarting the platform.