connecting gmx account to outlook fails....

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Hi @Thomas Steger 

Thank you for sharing the details of your situation. This helps me better understand what you are experiencing. 

Based on my research regarding Setting Up Outlook (IMAP), the incoming server should be set to imap.gmx.com. 

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If your email address ends with .net, you may also try replacing .com with .net for the server setting to see whether that applies to your situation. Since the incoming server value was not mentioned earlier, could you please confirm whether you are currently using the same configuration? 

To better understand your setup, may I also clarify the following: 

1. Which Classic Outlook version are you using, Outlook for Microsoft 365 or a specific Outlook 20xx version? 
2. Are you still able to access your email through the web interface? 
3. If applicable, do you have another IMAP account available to test whether it can be added successfully to Classic Outlook? 

If I have misunderstood any part of your situation, or if you have updates to share, please feel free to reply. Thank you for your time and cooperation. 

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The SMTP connection failure indicates that the Outlook account settings do not match what the server expects, or the connection is being blocked.

Try the following in Outlook for Windows (Classic):

1. Open the account settings dialog
   • Go to Control Panel → Mail → Email Accounts.
   • Select the GMX account and choose Change.
2. Verify server name, ports, and encryption
   • Ensure the Outgoing mail server (SMTP) is set to mail.gmx.net.
   • Click More Settings → Advanced.
   • Under Server Port Numbers, compare the Outgoing server (SMTP) port and encryption type with the values provided by GMX. If they do not match, manually change them.
   • GMX’s documentation must be followed exactly; if GMX requires a different port or encryption (for example, SSL/TLS instead of STARTTLS, or a different port number), update those values here.
3. Test the account settings
   • In the Change Account window, click Test Account Settings.
   • If red markers appear, some settings are still incorrect. Re-check the SMTP server name, port, and encryption type against GMX’s instructions and test again.
   • When all tests show green check marks, click Close, then Next, then Finish.
4. If problems persist
   • Contact GMX support or check GMX’s help pages to confirm the current SMTP server name, port, encryption type, and any special authentication requirements.
   • Also verify that POP/IMAP/SMTP access is fully enabled on the GMX side and that no firewall or network security software is blocking outbound SMTP connections.

References:

• Change or update email account settings in Outlook for Windows