Updated as of 1 March 2018:
To change your fonts, signature and other settings in Outlook 365/Outlook.com email, follow these steps:
- Click the Gear icon and type Options into the search box.
Select Message Options from the results.
In Office 365, you’ll find your messaging options on the left. Click on Layout. Change fonts from the Email signature and Message format sections.
In regular Outlook.com (aka if you are not under a company account), Email Signatures are under the Personalization tab and the Compose tab.
Yes, it’s ridiculous that there’s no real way to access the settings except by going through Search. The even more ridiculous part is that these settings were so hidden in the first place. For goodness sake, Microsoft, I should not need to write a post just so I can remember how to change my signature!