GMail API: Script works when run manually, but not when triggered

This was incredibly stupid, but in case it might help someone else in the future (it won't, because this level of stupidity is probably not replicable but):

In the original version of my script, the function isMyEx was declared in global scope* outside of doSend more or less like the following:

function isMyEx(draft) {
      var recipient = draft.getMessage().getTo();
      var isTheirEmail = /nameofmyex/.test(recipient);
      return isTheirEmail; };

function noSend(e) {  
  var drafts = GmailApp.getDrafts();
  var callback = function(draft) {
    if(isMyEx(draft)) {
      draft.update('', '', ''); 
      draft.deleteDraft(); 
    } else {  } };

  drafts.forEach(callback); return;
};

Since isMyEx was defined before noSend, when I clicked the button to set a trigger for the script, the default function to be triggered was the one to be defined first isMyEx. Which of course will throw the error that I described if it is called outside of doSend, instead of as a callback within.

_{*This is probably considered bad practice. If so, please understand that I did it out of ignorance, not out of some malicious intent to spread bad coding practices to the visitors of this web site. In particular, please don't yell at me. I've already served my punishment for this bad coding practice, since it has already come back to bite me in the behind, see below.}

Moral of the story: The triggers are not for the entire script. It is not only possible, but actually necessary to set a trigger for each function in the script individually. So if you don't bother to look at which function in the script you are setting the trigger for, don't be surprised like I was when you don't get the desired results.

I only figured this out because, after putting the definition of isMyEx inside of noSend (and then inside of callback), when I clicked the trigger button of the script again, there was a red message below the trigger Selected function not found. This didn't make sense to me at first, since I thought the trigger was for the entire script, but then I looked at the buttons more carefully and realized that it meant that the trigger was only trying to run the function isMyEx, not the entire script file (which I guess would make sense for much larger scripts). Anyway, after moving isMyEx from global scope, it made sense that the function could no longer be found.

Anyway, after I changed the trigger to be for noSend instead of isMyEx, everything works fine/perfectly with the automatic trigger, not just when I run the script manually.