The editor offers more fonts than your guests will actually see. Gmail, Outlook, and other email clients restrict which fonts they will render, and an imported font such as Montserrat will not display unless the recipient happens to have it installed on their device. For that reason, use email-safe fonts.
What email-safe fonts are
Email-safe fonts, also called web-safe fonts, are the typefaces supported by every major email client. They will render as you intended no matter which client your guest opens the message in.
The email-safe fonts to use
Arial
Courier
Courier New
Georgia
Helvetica
Helvetica Neue
Lucida
Tahoma
Times
Times New Roman
Trebuchet MS
Verdana
All of these are easy to read. Georgia, Verdana, and Trebuchet MS are among the most readable at small sizes.
Why the font can still change
Support for web fonts, which are not the same thing as web-safe fonts, varies by email client. Some clients override your choice entirely regardless of what you set:
Gmail on Android defaults to Roboto, and on iOS renders closer to Helvetica.
Some Android clients override fonts to Roboto as the default sans-serif.
Sticking to the list above is the only reliable way to keep control of how your emails look.
Further reading
Getting help
Open Talk to Us in the left menu of the platform, or email support@bookboost.io.