Every time I log on to my webmail I see a bar like on image below. I don't want to add this as an application and it is pretty annoying to close this every time. How can I disable it permanently?

The bar says this: example

I tried to use Firebug to see what causes this bar to appear but with no luck. Anyone help?


Su's answer from http://webmasters.stackexchange.com :

This is done by registering a protocol handler. From that page:

navigator.registerProtocolHandler("mailto", "https://www.example.com/?uri=%s", "Example Mail");

The site would just have to run a similar snippet at an appropriate moment(login, in your case).

Link: registering a protocol handler

How can this be blocked?

  • That sounds like something coming from your webmail. Have you tried looking in your webmail settings to see if you can disable it?
    – SaintWacko
    Dec 2 '11 at 17:21
  • I know that my webmail might send something to Firefox in order to display this. I want make Firefox ignore this.
    – Jan Ajan
    Dec 3 '11 at 9:42
  • 1
    I'm not having much luck figuring out how the webpage might request it. If you can find out, you might be able to block it using something like Ad-Block Plus.
    – SaintWacko
    Dec 5 '11 at 16:17
  • you could probably also write a Greasemonkey userscript that selectively overrides whatever Javascript functionality on the page that is trying to register itself as a mailto handler..
    – merv
    Mar 3 '12 at 11:06
  • As some Firefox settings are OS-dependent, the answer may depend on your OS too. So can you specify your operating system and the Firefox version.
    – fiktor
    Sep 5 '12 at 8:52

have you tried going to about:config

There are some keys in there relating to mailto:


You could try toggling them, I can't test as I can't recreate whats happening for you, I think maybe the first of the three to false maybe a good start,

Be careful when editing this config as it may cause strange things to happen maybe even break firefox.

  • 20
    This recently just happened to me, after over 15 years of using it. Changing network.protocol-handler.external.mailto to false seems to have worked for me.
    – Asinine
    Sep 21 '20 at 21:12
  • 4
    This did the trick for outlook365 and FF 89.
    – Alfabravo
    Jul 7 '21 at 14:01
  • 1
    Only setting the network.protocol-handler.external.mailto preference to false was needed in Firefox 94 (Tutanota webmail, Linux).
    – user598527
    Nov 11 '21 at 18:10

… disable it permanently?

Mozilla bug 668577 - registerProtocolHandler notification should provide a "don't ask me again" button draws attention to How to hide/disable Firefox notification for addon/application | Firefox Support Forum | Mozilla Support (2011-06-30))

https://github.com/MrAlex94/Waterfox/issues/680#issuecomment-401004043 gives a (legacy) Stylish 2.1.1 workaround that's effective for:

Add Tutanota

Add o2 Poczta

For this case, you could try:

@namespace url(http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul);

Adapted from https://support.mozilla.org/questions/994658#answer-556629 
for https://superuser.com/q/363827/84988

notification[label^="Add o2 Poczta"][value="Protocol Registration: mailto"] {
  display: none !important; 

Firefox Quantum might require a different approach but the essence of the workaround should be the same; styling.


Another little bad news, because Mozilla has made another change that's why now it didn't work with Firefox-v70.

As you can probably guess, apparently the file "userContent.css" can't rectify this trouble anymore... And no I wasn't able to find another solution even with the file "userChrome.css" But at least, it could be reactivate :

## How to remove the button close on every tabs ?
## Just recopy this example inside the "userChrome.css"
@-moz-document url(chrome://browser/content/browser.xhtml)
    .tab-close-button {display:none !important;}

So thank you @0x7c0 because I had found this solution :

## At this moment, the notification has vanished on the new website of Tutanota.
## Which can be reach only at this new adress : "https://mail.tutanota.com/login"
## That's right, now the previous adress : "https://app.tutanota.com/#login" doesn't seem to exist (at all).
## I will assume Tutanota has probably made the choice to remove it.

PS : For the record and for once reddit was hepful.


This looks like it has been a persistent bug in Firefox for ~10 years.

There's also a more recently raised bug with a broader scope that might encompass this one.

The only solution I have found ([1],[2]) has the unfortunate side-effect of disabling the operation of all mailto links.

  1. open new tab page address: about:config
  2. find variable: network.protocol-handler.external.mailto
  3. double-click it to set to false

It insists on being added, right? So try the following.

  • Add it.
  • Got to Firefox Settings / General / Applications.
  • You will see that next to mailto there is a combo box of options to handle mailto links. That which you just added is in the list of options. Most probably it is the selected option.
  • Just choose another one; the one which was selected before the first step.

As a result

  • the message will never appear again (since you clicked Add Application in the first step),
  • Firefox will operate as before (since in the last step you chose the mailto app, which was in use before the first step).

Definitely the message should contain a "Don't ask me again" option, which is a bug in Firefox, as Danny Garside pointed out.

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