app/views/subscription_mailer/send_digest.html.erb
<header style="text-align: center;color:black">
<img src="https://avatars2.githubusercontent.com/u/4621650?s=200&v=4" style="width: 100px;height: 100px">
<p style="font-size: 20px">[Public Lab] <%= @subject %></p>
<p><%= Time.now.strftime("%B %-d %Y") %></p>
</header>
<div style="width:95%;margin: 0 auto;margin-top: 54px;color: black;">
<p style="font-size: 1.2em; font-family: sans-serif;margin-bottom: 0;color: lightgray;"><%= translation('subscriptions.digest.based_on_follow')%></p>
<%= render partial: "subscriptions/digest"%>
</div>