Did you try another Browser to verify it wasn't a server error? That would be the best way to know where the problem is.

I can send emails to hotmail from any other browser. It only fails when I send one from Thunderbird. This has been the same for about three weeks now and it's causing me a lot of hassle as I use Thunderbird as my business email address. Does anybody know what I can do to resolve this please?

If you use a bookmark then navigate to the web page starting with the main page or the sign in page in case there is a problem with this bookmark.

You can try these steps in case of issues with web pages:

You can reload web page(s) and bypass the cache to refresh possibly outdated or corrupted files.

• hold down the Shift key and left-click the Reload button
• press "Ctrl + F5" or press "Ctrl + Shift + R" (Windows,Linux)
• press "Command + Shift + R" (Mac)

Clear the Cache and remove the Cookies from websites that cause problems via the "3-bar" Firefox menu button (Options/Preferences).

"Remove the Cookies" from websites that cause problems:

• Options/Preferences -> Privacy & Security
  Cookies and Site Data -> Manage Data

"Clear the Cache":

• Options/Preferences -> Privacy & Security
  Cookies and Site Data -> Clear Data -> Cached Web Content: Clear

Start Firefox in Safe Mode to check if one of the extensions ("3-bar" menu button or Tools -> Add-ons -> Extensions) or if hardware acceleration is is causing the problem.

• switch to the DEFAULT theme: "3-bar" menu button or Tools -> Add-ons -> Appearance
• do NOT click the "Refresh Firefox" button on the Safe Mode start window

• https://support.mozilla.org/en-US/kb/troubleshoot-firefox-issues-using-safe-mode
• https://support.mozilla.org/en-US/kb/troubleshoot-extensions-themes-to-fix-problems

flinchwymer said

Whenevr I send an email to a hotmail address it bounces back with this message. 550 5.7.1 Unfortunately, messages from [5.77.60.165] weren't sent. Please contact your Internet service provider since part of their network is on our block list (S3140). You can also refer your provider to http://mail.live.com/mail/troubleshooting.aspx#errors. [VE1EUR01FT043.eop-EUR01.prod.protection.outlook.com] Can anybody help please?

I would suggest you do exactly what the message says and contact you email provider, be that your ISP or some other mail provider like google or yahoo. Basically your mail server is blacklisted (probably for sending spam) There is nothing I can do about that and your options are limited to contact those that provider the email service. Not those who provide the email client.