I think this is happening here:

#+BEGIN_SRC emacs-lisp
(org-export-string-as "\\begin{displaymath}
  \\int   f dx =0
\\end{displaymath}"
     'html t )
#+END_SRC

#+RESULTS:
:
: <div class="equation-container">
: <span class="equation">
: <img src="ltximg/latex1pIlij_8e5abfd22f18b9fd072a0f1273f49cd3a35040d3.png" alt="latex1pIlij_8e5abfd22f18b9fd072a0f1273f49cd3a35040d3.png" />
: </span>
: <span class="equation-label">
: 1
: </span>
: </div>


#+BEGIN_SRC emacs-lisp
(org-export-string-as "$e^x$"
     'html t )
#+END_SRC

#+RESULTS:
: <p>
: <img src="ltximg/latex4ckMGO_c7e2801d6583d97def1ae1189f6c1ecf1db0d41b.png" alt="latex4ckMGO_c7e2801d6583d97def1ae1189f6c1ecf1db0d41b.png" /></p>

John

-----------------------------------
Professor John Kitchin 
Doherty Hall A207F
Department of Chemical Engineering
Carnegie Mellon University
Pittsburgh, PA 15213
412-268-7803

@johnkitchin
http://kitchingroup.cheme.cmu.edu

On Fri, Nov 1, 2019 at 9:59 AM Uwe Brauer <oub@mat.ucm.es> wrote:

>>> "JK" == John Kitchin <jkitchin@andrew.cmu.edu> writes:

   > I also see this. I wonder if you use any scimax functions?

Good I am relived, I thought it was just me

   > Do you see any advice on org-create-formula-image:

   > C-h f org-create-formula-image
no

,----
| org-create-formula-image is a compiled Lisp function in
| ‘~/ALLES/emacs/site-lisp/packages/org/org.el’.
|
| (org-create-formula-image STRING TOFILE OPTIONS BUFFER &optional
| PROCESSING-TYPE)
|
| Create an image from LaTeX source using external processes.
|
| The LaTeX STRING is saved to a temporary LaTeX file, then
| converted to an image file by process PROCESSING-TYPE defined in
| ‘org-preview-latex-process-alist’.  A nil value defaults to
| ‘org-preview-latex-default-process’.
|
| The generated image file is eventually moved to TOFILE.
|
| The OPTIONS argument controls the size, foreground color and
| background color of the generated image.
|
| When BUFFER non-nil, this function is used for LaTeX previewing.
| Otherwise, it is used to deal with LaTeX snippets showed in
| a HTML file.
`----

But I have this
,----
|
| org-mime-htmlize is an autoloaded interactive compiled Lisp function
| in ‘~/ALLES/.emacs.d/elpa/org-mime-20190805.57/org-mime.el’.
|
| It is bound to <C-f31>, <C-next>.
|
| (org-mime-htmlize)
|
| This function has :around advice: ‘ad-Advice-org-mime-htmlize’.
|
| Export a portion of an email to html using ‘org-mode’.
| If called with an active region only export that region, otherwise entire body.
|
|
`----


I wounder what that is about, @Eric, do have also this setting? John?