Hello,
I cannot send email from my personal Outlook.de account in Thunderbird, although receiving email works. Sending email from the same account through Outlook.com in … (ler mais)
Hello,
I cannot send email from my personal Outlook.de account in Thunderbird, although receiving email works. Sending email from the same account through Outlook.com in a web browser also works.
This is a personal Microsoft account, not a business or school account. I do not have access to an Exchange Online or Microsoft 365 administration console.
Environment:
- Thunderbird version: 158.0.1 (the version reported when troubleshooting started)
- Operating system: Windows 11
- Email provider: Outlook.com / Outlook.de
Outgoing server settings:
- Server: smtp-mail.outlook.com
- Port: 587
- Connection security: STARTTLS
- Authentication method: OAuth2
- Username: full Outlook.de email address
OAuth2 was already configured before the problem was investigated.
When I try to send an email, Thunderbird displays an authentication failure. A Microsoft sign-in page briefly opens and closes, after which the same error appears again.
The Thunderbird Error Console reports:
mailnews.smtp: Command failed: 535 Authentication unsuccessful, SmtpClientAuthentication is disabled for the Mailbox.
It also shows:
currentAction=_actionAUTH_XOAUTH2
A second entry reports:
mailnews.smtp: Authentication failed: Authentication unsuccessful, SmtpClientAuthentication is disabled for the Mailbox.
Troubleshooting already performed:
1. Verified the SMTP server, port, STARTTLS, OAuth2 and username.
2. Removed the saved Microsoft/Outlook authentication entries for this account.
3. Completely closed and restarted Thunderbird, then retried authentication and sending.
4. Checked the cookie exceptions list: no exceptions were present.
5. Confirmed that sending through Outlook.com in a browser works.
Removing the saved authentication entries and signing in again did not resolve the issue.
My questions:
- Is this a known issue with personal Outlook.com/Outlook.de accounts?
- Is there any supported Thunderbird-side fix for this specific server response?
- Is a different supported account connection method available for this personal account that does not depend on SMTP AUTH?
- If Microsoft must change something on the server side, what exactly should I ask Microsoft Support to investigate?
I have found Microsoft's documentation about enabling SMTP AUTH in Exchange Online, but its administrator instructions do not apply to my personal Outlook.de account.
I can provide a screenshot of the Thunderbird Error Console.
Thank you for your help.