Comment # 3 on bug 1172800 from Wolfgang Bauer

(In reply to Axel Braun from comment #2)
> Is this related to this thread as well?
> https://lists.opensuse.org/opensuse-support/2020-06/msg00011.html

Hard to say without seeing the screenshot...

This bug report is about the mail headers though, not about (missing) fonts in
the mail body.
But if your problem is about smilies not being displayed as images anymore as
the reply suggests, it would probably indeed be a similar problem (the
underlying problem here was that QtWebEngine 5.15 didn't load local image and
css files anymore, the code had to be adjusted to allow that), and might be
fixed as well (there are a couple of similar fixes in the 20.04.2 release) but
I'm not sure.

The update should be in Tumbleweed in a couple of days anyway, so I'd suggest
to wait for that and if it still doesn't work file a new bug report upstream.