Yahoo Mail Ignores Your Font? Remove the Quotes

The fix: write font names without quotes

Yahoo Mail on the web throws away an inline font-family when the list contains a quoted name. It drops the whole declaration, not just the quoted font, so the fallbacks after it are lost too:

<!-- Yahoo Mail drops this whole declaration -->
<td style="font-family:'Courier New',Courier,monospace;">
  npm install --save-dev emailens
</td>

Font names made of plain words do not need quotes in CSS. The same list without them is valid and Yahoo keeps it:

<!-- Same fonts, no quotes: Yahoo keeps it -->
<td style="font-family:Courier New,Courier,monospace;">
  npm install --save-dev emailens
</td>

Keep the quotes only for a name that needs them, one with a digit at the start or a character other than letters, digits, hyphens and spaces. If your font needs them, set it in a <style> class instead: Yahoo kept the quoted list there.

<style>
  .code { font-family: 'Courier New', Courier, monospace; }
</style>
<!-- A class keeps the font in Yahoo, quotes and all -->
<td class="code" style="font-family:Courier New,Courier,monospace;">

What we tested

We sent one test email to a real Gmail inbox and a real Yahoo Mail inbox, both opened on the web in Chrome, on 28 October. Each row sets the same text in a different way. In a monospace font, iiiii and WWWWW take the same width, so a lost font is easy to see.

• Lost in Yahoo: any inline list with a quoted name, whether it came first ('SFMono-Regular',Consolas) or later (Consolas,'Liberation Mono').
• Kept in Yahoo: the same fonts unquoted, the generic monospace alone, !important, the font on a <td>, <code> and <pre> with no style, and a quoted list in a <style> class.
• Gmail kept every row. Its web app does not load web fonts, so it used the fallbacks, as expected.

What it looks like in a real newsletter

A monospace newsletter theme sets its font twice: in a <style> block for headings, and inline on the content table for everything else. Its inline list starts with the web font's quoted name. In Yahoo, the headings keep the theme; the body text, links, tip box, button, list and footer do not.

Common font stacks hit this without anyone choosing a special font: the system stack quotes 'Segoe UI', serif stacks quote 'Times New Roman'. Each works without quotes:

Your web font, if you load one with @font-face, still needs its fallbacks: Gmail and Outlook do not load it. See which email clients load web fonts.

Why support tables do not show it

Support data, ours included until this week, rates font-family as supported in Yahoo Mail, and the property itself is. What breaks is one way of writing its value, inline and with quotes, which a per-property table has no row for. We found it while testing emails that AI agents wrote for a newsletter app: the code blocks in a developer digest lost their monospace in Yahoo only.

Emailens now flags it. A quoted font list in an inline style raises a Yahoo Mail warning with the unquoted fix, and the Yahoo preview drops that font the way Yahoo does. Paste your email into the HTML email checker to see if yours has it.