Can someone here comment on why creating &amp; maintaining a solid local desktop email client is such a costly, moving target, such that it has required an organization the size of Mozilla to pursue it and get it &quot;nearly&quot; right?  Is the bulk of Thunderbird maintenance work happening in its &quot;HTML render&#x2F;js component(s)&quot;?  If so, could we stabilize on a Thunderbird without HTML render&#x2F;js support, providing it only as optional add-on?