'''Fix what? ''' You have shown us nothing. I ran a test with hotmail and it appears to work for me. see screenshot https://sites.google.com/view/new-sites-testing/links/mailto-link

  * Scroll to the section Applications.
  * In the search box, type mailto — you’ll see “mailto” appear as a content type.
  * In the Action column, click the drop-down.
  *  By default, you’ll see options like:

   * Use Gmail
   * Use Yahoo! Mail
   * Use AOL Mail
   *  Use other…

 "handlers": [
   {
     "name": "AOL Mail",
     "uriTemplate": "https://mail.aol.com/webmail-std/en-us/suite#/compose?to=%s"
   },
   ...
 ],
 "default": "AOL Mail"

I will explain so even you can understand. I have email provided by Verizon (my ISP), so my address is abc@verizon.com. However, Verizon requires that I use AOL mail as the email platform. My problem is that under Firefox the mailto function does not work correctly with AOL email (web version). I can identify AOL under Firefox but the mailto function simply opens the AOL link showing the default view. The goal is when you invoke the process to mail a site you are currently viewing, Firefox should open a new email in AOL Mail’s compose window with the site link in the body -- it simply opens the desktop email client. This is defined in Firefox under settings as follows: 1. Open Firefox’s Handlers settings 2. In Firefox’s address bar, type: * Scroll to the section Applications. * In the search box, type mailto — you’ll see “mailto” appear as a content type. * In the Action column, click the drop-down. * By default, you’ll see options like: 3. Always ask * Use Gmail * Use Yahoo! Mail * Use AOL Mail * Use other… I selected use AOL email, but when I attempt to use the mailto function is simply opens my AOL email. It should open, and compose a new email with the subject defined and the URL of the web site I am viewing in the body. For that to occur, you need the string "mailto","https://mail.aol.com/d/compose/?to=%s#newtab","AOL Mail"); The current settings of Firefox lock the capability to modify that string. I have attempted to modify the uriTemplate value as follows: "mailto": { "handlers": [ { "name": "AOL Mail", "uriTemplate": "https://mail.aol.com/webmail-std/en-us/suite#/compose?to=%s" }, ... ], "default": "AOL Mail" } As that capability is locked, my issue is how can that be modified. Ideally, selecting the AOL Mail as an option under the mailto settings should produce correct code, and it does not. There are not any screen shots which would further clarify the issue -- try AOL Mail as an option and view the string and the issue will be obvious. Please escalate as needed as there are many customers who use Verizon as their ISP and have been forced into this model. Thank you.