https://support.office.com/client/Settings-for-POP-and-IMAP-access-for-Office-365-for-business-or-Microsoft-Exchange-accounts-7fc677eb-2491-4cbc-8153-8e7113525f6c?ui=en-US&rs=en-US&ad=US&fromAR=1

that page suggests the port is 578 with TLS.

I think he means port 587. :)

Thanks, but I still cant send emails... Now I've tried to use: port: 587 servername: smtp.outlook.com TLS

Do anyone else have an idea on what to do to solve this problem?

Outgoing (SMTP) Server

Server address: smtp-mail.outlook.com

 Port: 25 (or 587 if 25 is blocked)

Authentication: Yes

 Encrypted Connection: TLS

User name: Your email address

Password: Your password

This is what they recommend for server settings.

Is your firewall blocking Thunderbird. It needs to be set to Allowed.

Thanks for your answer and I tried it, but I still cant send emails :(

I use thunderbird for my gmail and 2 more mailaccounts and there is never a problem...think that the firewall is accepting thunderbird because it works with them

To diagnose problems with Thunderbird, try one of the following:

• Restart Thunderbird with add-ons disabled (Thunderbird Safe Mode). On the Help menu, click on "Restart with Add-ons Disabled". If Thunderbird works like normal, there is an Add-on or Theme interfering with normal operations. You will need to re-enable add-ons one at a time until you locate the offender.
• Restart the operating system in safe mode with Networking. This loads only the very basics needed to start your computer while enabling an Internet connection. Click on your operating system for instructions on how to start in safe mode: Windows 8, Windows 7, Windows Vista, Windows XP, OSX

If safe mode for the operating system fixes the issue, there's other software in your computer that's causing problems. Possibilities include but not limited to: AV scanning, virus/malware, background downloads such as program updates.

Are you getting an error message when trying to send?

Did you notice the different SMTP address from the outlook site from what you showed?

Hi again! This is the message I get when trying to send: Sending of message failed. The message could not be sent because the connection to SMTP server smtp-mail.outlook.com timed out. Try again or contact your network administrator.

And I saw the different SMTP adress and thought the problem was solved... :(