I did email Mailcow as I could not understand German language, have not heard from them.
Have you seen Modoboa? https://modoboa.readthedocs.io/en/1.2.0/plugins/webmail.html It is interesting because it could show where the text editor bolts on the webmail client gui’s :
"Now, each user has the possibility to choose between CKeditor and the raw text editor to compose their messages."
There is on webmail gui client, perhaps there is on Miab’s Roundcube:
- text editor for example, CKeditor (these Foss & opensource text editors are easily customizable)
- raw editor
There is a location in the code about placing the text editor like this on Modoba (and perhaps because it’s Foss & opensource also on Miab’s Roundcube like so) :
"Modoboa supports CKeditor to compose HTML messages. To use it, first download it from the official website, then extract the tarball:"
$ cd <modoboa_site_dir>
$ tar xzf /path/to/ckeditor/tarball.tag.gz -C sitestatic/js/
"And you’re done!"