To set a custom zoom level, press the Custom scaling link (Windows 10 Version 1709) or the Advanced scaling settings link (Windows 10 Version 1803). If you find that a different key/Mouse combination works for you, please share it here so others can benefit. In the Scale and layout section, use the Change the size of text, apps, and other items dropdown list to set your preferred zoom level.
I have tested this fix on a Dell laptop running Windows 10. The key combination you may have to press to get 100% font Zoom factor may differ on your laptop. This fix also works if your Outlook font in Reply Mode has increased, just reduced it to 100% with the same steps. This should fix your font changing to very small size when you are replying to an email in Outlook. Or, while holding the “Ctrl” key down, pinch the mouse pad on your laptop in or out to get 100% Zoom factor.If you are using a mouse with a scroll wheel, scroll the wheel up or down to increase the Zoom to 100%.Your options are New mail messages, Replying or forwarding. Specify a font size on the Format Text tab in the Font group. Open Font in the section that contains the font you want to change. Select the text that you want to change, and then on the ribbon, do one of the following: Specify a font size on the Message tab in the Basic Text group. Regards, Steve Fan Please remember to mark the replies as answers if they helped. See The text of my email messages is larger or smaller than usual for more details. After clicking, pick a zoom percentage, and then check the box marked Remember my preference. Replying or forwarding messages - You can have a. New mail messages - Sets the default font for original messages you compose. Go to File > Options > Mail > Stationery and Fonts. Hold down the “Ctrl” key on your keyboard Click or tap the Mail category on the left side. To set a zoom percentage, click on at the bottom right corner of the Zoom control. When you set a default font, every new message you create uses that font setting default.The Fix for Outlook Font Size Change in Reply Mode The Zoom factor in the Reply Mode is what you need to increase to 100%. The fix for Outlook font size when it changes to very small size when you are replying to an email is really very simple, and I have summarized it below. Many people have tried increasing their Outlook font size in reply mode up to size 18 or 20, just so they can read what they are typing, but only to find out to their dismay that when they send the message without reducing the font back to the normal setting, the recipients of their reply get the message in VERY large size 18 or 20 font! This has happened to me when the size of my font is at 11 in the tool bar, but any message I type when replying to an email is like font size 6. When you are replying to an email you received in Outlook, you may find that the size of the font in the message you are typing is so small that you can barely see what you have typed, even though the font size in your tool bar has not changed. Provide an option to allow font size to be changed or customized and same in Microsoft Outlook 2016 Community You can change the fonts and font sizes in the Message list and zoom the reading pane or opened messages.