First of all, i am not sure if this has already been fixed in more modern versions of kmail (using Debian Stable here). STEPS TO REPRODUCE 1. Compose an email in HTML mode with, let's say Noto Sans at 11 points of size 2. Make text bigger or smaller for viewing (Ctrl+Mouse scroll wheel, or Ctrl+{,+}) 3. Send message 4. Received message will have a font size proportional to the zoom you used composing the message It's also notable that when kmail receives emails composed like this (a CC for yourself) the size of the text will appear normal so you won't notice but other people with different emails clients will In my mind, zoom of the text should be independent of the font size sent in the HTML. But that's my two cents OBSERVED RESULT Example of the HTML code generated by the composer </style></head><body style=" font-family:'Noto Sans'; font-size:31pt; font-weight:400; font-style:normal;"> EXPECTED RESULT </style></head><body style=" font-family:'Noto Sans'; font-size:11pt; font-weight:400; font-style:normal;"> SOFTWARE/OS VERSIONS Linux/KDE Plasma: Debian Stable 10.3 KDE Plasma Version: 5.14.5.1 KDE Frameworks Version: 5.54.0 Qt Version: 5.11.3+dfsg1 ADDITIONAL INFORMATION
<body><p style="margin-top:0;margin-bottom:0;margin-left:0;margin-right:0;">Sdfsfdfdf <span style="font-size:1.2em;"> sqdqs dqsdqsdqsdqsd q </span></p> => 1.2em now. so it depends against zoom. it's fixed from long time ago. 5.9.3 is very old :)