Since version 5.0, there is a "Suppress hidden elements of documents" option under Internet Options->Email, which controls what to do with hidden stuff of documents when sending it in Emails [1]. However, help still does not mention it: https://help.libreoffice.org/7.4/en-US/text/shared/optionen/01020300.html?&DbPAR=SHARED&System=UNIX Additionally, based on bug 152139, that help page might need shown on Windows, too. Getting Started Guide helpfully discusses it, and it includes it on the screenshot: https://documentation.libreoffice.org/assets/Uploads/Documentation/en/GS7.3/GS73-GettingStarted.pdf#page=63 [1] https://wiki.documentfoundation.org/ReleaseNotes/5.0#Maintaining_invisible_content_in_Emails