Start Firefox in Safe Mode {web link} by holding down the <Shift> (Mac=Options) key, and then starting Firefox.

A small dialog should appear. Click Start In Safe Mode (not Refresh). Is the problem still there?

I've done this before as well and it would work for one or two emails then back to the way it was.

Many site issues can be caused by corrupt cookies or cache.

• Clear the Cache and
• Remove Cookies

Warning ! ! This will log you out of sites you're logged in to. You may also lose any settings for that website.

• Cookies; Delete cookies to remove the information websites have stored on your computer {web link}

• Cache; How to clear the Firefox cache {web link}

If there is still a problem, Start Firefox in Safe Mode {web link} by holding down the <Shift> (Mac=Options) key, and then starting Firefox.

A small dialog should appear. Click Start In Safe Mode (not Refresh). Did this help?

While you are in safe mode;

Try disabling graphics hardware acceleration in Firefox. Since this feature was added to Firefox it has gradually improved but there are still a few glitches.

How to disable Hardware Acceleration {web link}

Do I have to use FireFox in safe mode for ever?

ardenfan said

Do I have to use FireFox in safe mode for ever?

Firefox's Safe Mode is a diagnostic tool. By seeing whether there is any difference between a site's functionality in regular and in safe mode, we can start to narrow down potential causes of problems.

Did you notice any difference?

Firefox's Safe Mode:

• disables all Extensions (most common issue)
• disables Hardware Acceleration (for graphics and video, probably not relevant here)
• disables userChrome.css/userContent.css customization files (probably not relevant here)
• disables the JavaScript compilers

I could send an email after doing all above while in safe mode. Once I restarted I couldn't send an email.

So a possible reason for that is interference by one of your extensions. Could you review and consider whether any might block any content or connections:

You can view, disable, and often remove unwanted or unknown extensions on the Add-ons page. Either:

• Ctrl+Shift+a (Mac: Command+Shift+a)
• "3-bar" menu button (or Tools menu) > Add-ons
• type or paste about:addons in the address bar and press Enter/Return

In the left column of the Add-ons page, click Extensions.

Then cast a critical eye over the list on the right side. Any extensions Firefox installs for built-in features are hidden from this page, so everything listed here is your choice (and your responsibility) to manage. Anything that looks as though it could affect connections or block content? If in doubt, disable (or remove).

Any improvement?

There were no extensions and I've added the image of the add ons. I assume I can get rid of these.

I chose never activate on all three and I still couldn't send an email.

No Extensions?

The Plugins are not disabled in Firefox's Safe Mode, so those are not "suspects" for causing this problem.

Could you check your connection setting here:

• Windows: "3-bar" menu button (or Tools menu) > Options
• Mac: "3-bar" menu button (or Firefox menu) > Preferences
• Linux: "3-bar" menu button (or Edit menu) > Preferences
• Any system: type or paste about:preferences into the address bar and press Enter/Return to load it

In the search box at the top of the page, type proxy and Firefox should filter to the "Settings" button, which you can click.

The default of "Use system proxy settings" piggybacks on your Windows/IE "LAN" setting. "Auto-detect" can lead to a flaky connection. You may want to try "No proxy".

Any difference?

I tried no proxy and still couldn't send an email. I didn't do it in safe mode though.

no extensions.. is that a bad thing? I uploaded the image

It didn't work in safe mode either

ardenfan said

It didn't work in safe mode either

Wait, what? I thought it did when you said --

ardenfan said

I could send an email after doing all above while in safe mode. Once I restarted I couldn't send an email.

So did anything on this page help so far?

After I chose the no proxy and opened it in safe mode my email would not go.

Late to this but are we talking web outlook or MS outlook? If Web Outlook I think you should use IE if your O/S is Windows. I seen where functions of outlook will not work with other Browsers but in IE they will work correctly.

Thanks and It is web but I've ALWAYS used firefox and would like to continue to. It's odd that all of a sudden both my computer and laptop no longer will work to send emails. Everything else is fine.

Could you try:

Private Window Test

Most likely, you use "regular" browsing, where Firefox accumulates history. To check whether accumulated data could be causing the issue, try using Outlook in a Private Window. You can launch that using either:

• "3-bar" menu button > New Private Window
• Ctrl+Shift+p
• right-click https://outlook.live.com/mail/inbox/ and choose Open Link in New Private Window

Any difference in your ability to send a message?

If the Private Window Test didn't help:

New Profile Test

This takes about 3 minutes, plus the time to test Outlook.

Inside Firefox, type or paste about:profiles in the address bar and press Enter/Return to load it.

Click the Create a New Profile button, then click Next. Assign a name like Nov2018, ignore the option to relocate the profile folder, and click the Finish button.

After creating the profile, scroll down to it and click the Set as default profile button below that profile, then scroll back up and click the Restart normally button. (There are some other buttons, but please ignore them.)

Firefox should exit and then start up using the new profile, which will just look brand new. Please ignore any tabs enticing you to connect to a Sync account or to activate extensions found on your system so we can get a clean test.

Can you send emails in the new profile?

If so, try exiting out of Firefox and starting it up again to make sure it still occurs on the second run. If it does, there may be an issue with settings in your regular profile.

When you are done with the experiment, open the about:profiles page again, click the Set as default profile button for your normal profile, then click the Restart normally button to get back to it.

I've done both and I still can't send an email.

You get the same error messages in a new profile?

If you use Avast, AVG, Bitdefender, ESET or Kaspersky, could you try removing them as "man in the middle" of your browsing between Firefox and websites? This article lists the general steps: How to troubleshoot security error codes on secure websites.