The issue looks like to be with the email RTE (Rich Text Editor) your "email" entity is using. You can try this:
1. Create a JS web resource in your environment using the code snippet below:
{
"defaultSupportedProps": {
"advancedContent": true,
"contextmenuadditionslist": [{"name": "nativeContextMenuHint", "label": "To check spelling, open<br>native menu (Ctrl+right-click)."}],
"dialog_backgroundCoverColor": "black",
"disableNativeSpellChecker": false,
"enterMode": 3,
"extraPlugins": "computedfont,contextmenuadditions,emailrestoreinlineimages,superimage,copyformatting,tableselection,tabletools,tableresize,autolink,quicktable,blockquote,collapser,stickystyles,pastefromword",
"height": "600px",
"toolbarLocation": "top",
"fillEmptyBlocks": true,
"font_defaultLabel": "Calibri",
"font_names": "Angsana New/'Angsana New', 'Leelawadee UI', Sathu, serif;Arial/Arial, Helvetica, sans-serif;Arial Black/'Arial Black', Arial, sans-serif;Calibri Light/'Calibri Light', 'Helvetica Light', sans-serif;Calibri/Calibri, Helvetica, sans-serif;Cambria/Cambria, Georgia, serif;Candara/Candara, Optima, sans-serif;Century Gothic/'Century Gothic', sans-serif;Comic Sans MS/'Comic Sans MS';Consolas/Consolas, Courier, monospace;Constantia/Constantia, 'Hoefler Text', serif;Corbel/Corbel, Skia, sans-serif;Cordia New/'Cordia New', 'Leelawadee UI', Silom, sans-serif;Courier New/'Courier New';DaunPenh/DaunPenh, 'Leelawadee UI', 'Khmer MN', sans-serif;Franklin Gothic Book/'Franklin Gothic Book', 'Avenir Next Condensed', sans-serif;Franklin Gothic Demi/'Franklin Gothic Demi', 'Avenir Next Condensed Demi Bold', sans-serif;Franklin Gothic Medium/'Franklin Gothic Medium', 'Avenir Next Condensed Medium', sans-serif;Garamond/Garamond, Georgia, serif;Gautami/Gautami, 'Nirmala UI', 'Telugu MN', sans-serif;Georgia/Georgia, serif;Impact/Impact, Charcoal, sans-serif;Iskoola Pota/'Iskoola Pota', 'Nirmala UI', 'Sinhala MN', sans-serif;Kalinga/Kalinga, 'Nirmala UI', 'Oriya MN', sans-serif;Kartika/Kartika, 'Nirmala UI', 'Malayalam MN', sans-serif;Latha/Latha, 'Nirmala UI', 'Tamil MN', sans-serif;Leelawadee UI/'Leelawadee UI', Thonburi, sans-serif;Lucida Console/'Lucida Console', Monaco, monospace;Lucida Handwriting/'Lucida Handwriting', 'Apple Chancery', cursive;Lucida Sans Unicode/'Lucida Sans Unicode';Mangal/Mangal, 'Nirmala UI', 'Devanagari Sangam MN', sans-serif;Nirmala UI/'Nirmala UI', sans-serif;Nyala/Nyala, Kefa, sans-serif;Palatino Linotype/'Palatino Linotype', 'Book Antiqua', Palatino, serif;Raavi/Raavi, 'Nirmala UI', 'Gurmukhi MN', sans-serif;Segoe UI/'Segoe UI', 'Helvetica Neue', sans-serif;Shruti/Shruti, 'Nirmala UI', 'Gujarati Sangam MN', sans-serif;Sitka Heading/'Sitka Heading', Cochin, serif;Sitka Text/'Sitka Text', Cochin, serif;Sylfaen/Sylfaen, Mshtakan, Menlo, serif;TW Cen MT/'TW Cen MT', 'Century Gothic', sans-serif;Tahoma/Tahoma, Geneva, sans-serif;Times New Roman/'Times New Roman', Times, serif;Times/Times, 'Times New Roman', serif;Trebuchet MS/'Trebuchet MS';Tunga/Tunga, 'Nirmala UI', 'Kannada MN', sans-serif;Verdana/Verdana, Geneva, sans-serif;Vrinda/Vrinda, 'Nirmala UI', 'Bangla MN', sans-serif;メイリオ/Meiryo, メイリオ, 'Hiragino Sans', sans-serif;仿宋/FangSong, 仿宋, STFangsong, serif;微軟æ£é»‘é«”/'Microsoft JhengHei', 微軟æ£é»‘é«”, 'Apple LiGothic', sans-serif;微软雅黑/'Microsoft YaHei', 微软雅黑, STHeiti, sans-serif;新宋体/NSimSun, 新宋体, SimSun, 宋体, SimSun-ExtB, 宋体-ExtB, STSong, serif;新細明體/PMingLiU, 新細明體, PMingLiU-ExtB, 新細明體-ExtB, 'Apple LiSung', serif;楷体/KaiTi, 楷体, STKaiti, serif;標楷體/DFKai-SB, 標楷體, BiauKai, serif;游ゴシック/'Yu Gothic', 游ゴシック, YuGothic, sans-serif;游明æœ/'Yu Mincho', 游明æœ, YuMincho, serif;隶书/SimLi, 隶书, 'Baoli SC', serif;黑体/SimHei, 黑体, STHeiti, sans-serif;굴림/Gulim, 굴림, 'Nanum Gothic', sans-serif;ê¶ì„œ/Gungsuh, ê¶ì„œ, GungSeo, serif;ë‹ì›€/Dotum, ë‹ì›€, AppleGothic, sans-serif;ë§‘ì€ ê³ ë”•/'Malgun Gothic', 'ë§‘ì€ ê³ ë”•', AppleGothic, sans-serif;바탕/Batang, 바탕, AppleMyungjo, serif;바탕체/BatangChe, 바탕체, AppleMyungjo, serif;ï¼ï¼³ Pゴシック/'MS PGothic', 'ï¼ï¼³ Pゴシック', 'MS Gothic', 'ï¼ï¼³ ゴシック', 'Hiragino Kaku Gothic ProN', sans-serif;ï¼ï¼³ P明æœ/'MS PMincho', 'ï¼ï¼³ P明æœ', 'MS Mincho', 'ï¼ï¼³ 明æœ', 'Hiragino Mincho ProN', serif",
"fontSize_defaultLabel": "11",
"fontSize_sizes": "8/8pt;9/9pt;10/10pt;11/11pt;12/12pt;14/14pt;16/16pt;18/18pt;20/20pt;22/22pt;24/24pt;26/26pt;28/28pt;36/36pt;48/48pt;72/72pt;",
"copyFormatting_allowRules": true,
"qtStyle": { "border-collapse": "collapse", "font-size": "9pt" },
"qtCellBorderStyle": "solid",
"qtCellBorderWidth": "1px",
"qtCellSpacing": "0",
"qtCellPadding": "1",
"qtCellWith": "120px",
"qtCellBorderColor": "rgb(171, 171, 171)",
"pasteFilter": null,
"removePlugins": "autogrow,elementspath,image",
"skin": "superowa",
"stickyStyle": { "font-size": "11pt", "font-family": "'Calibri','Helvetica Neue',sans-serif" },
"toolbar":[{ "items": ["CopyFormatting", "Font", "FontSize", "Bold", "Italic", "Underline", "BGColor", "TextColor", "BulletedList", "NumberedList", "Outdent", "Indent", "Blockquote", "JustifyLeft", "JustifyCenter", "JustifyRight", "Link", "Unlink", "Superscript", "Subscript", "Strike", "Image", "BidiLtr", "BidiRtl", "Undo", "Redo", "RemoveFormat", "Table", "A11yshortcuts", "UserPersonalization"]}]
},
"disableImages": false,
"disableDefaultImageProcessing" : true,
"allowSameOriginSandbox": true,
"showFullScreenExpander": true,
"disableContentSanitization":true,
"readmodeCustomHandler": "WebResources/Activities/SystemLibraries/msdyn_EmailReadModeCustomHandler.js",
"sanitizerWhitelist": {
"attributes": [
"data-attachment-id"
]
},
"externalPlugins": [
{
"name": "emailrestoreinlineimages",
"path": "/WebResources/Activities/SystemLibraries/msdyn_RTEemailrestoreinlineimagesplugin.js"
}
]
}
2. Open your email entity and then main form.
3. Change the static value of the RTE to the web resource you just created.
4. Save and Publish the changes.
Additionally, you can play with the JS script to have default font - size, style etc and also do other customisation:
Reference: https://learn.microsoft.com/en-us/power-apps/maker/model-driven-apps/rich-text-editor-control#customize-the-rich-text-editor-control
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If you have further questions, please feel free to contact me .
Best Regards,
MP