Editing an Mailbox configuration file I want to use Sublime Text to edit a text file within one of my installed Applications. The application I am trying to edit is Mailbox. I have been trying to edit the following file - /Applications/Mailbox (Beta).app/Contents/Resources/compose.css.txt. I have been trying to rewrite the css on lines 21 to 25

body {
   background-color: transparent;
   font-family: "Helvetica Neue", san-serif;
   font-size: 14px;
   margin:0; }


When I change the typeface to comic sans for example, mailbox stops functioning. Is there a way to make this change without corrupting the application?

An image of the error after editing the txt file has been embedded below;
From what I could tell, Mailbox now stays open after it displays the message, and crashes.

Since the crash had a bunch of JSON processes in it, I figured maybe that the lines were encoded, and since Comic Sans MS does not have the same number of letters as Helvetica Neue, I figured that was the problem. I then changed Neue to Bold, and made it the same number of letters.

Since it stil crashed, I believe it is not actually corrupted. I believe there is a encoded hash, or some sort, in the binary. Since the edit changed the hash, that may be the problem.

TL;DR: It is not possible unless you patch the binary in some way.