In order to zoom in on the text of the Email App in Firefox OS double tap on the email message and use on finger to navigate around the screen. It is also possible to pinch to zoom on the screen.

In version 1.3, there currently is not a feature to enlarge the text. I apologize for the inconvenience.

Bug filed for feature: https://bugzilla.mozilla.org/show_bug.cgi?id=1076264

When you say e-mail listing, do you mean:

• The list of email messages where we display multiple messages in a list?
• The message reader where we display the contents of a single message (and double-tapping or pinch/zoom are available for some HTML messages through version 1.4 and all HTML messages for versions 2.0 onward.)