Hello Thunderbird Support, I have been trying for several days to add the email account info@gurmanservis.cz to the Thunderbird client on my Windows laptop, but I cannot complete the account verification. The following error message appears: “Authentication failed. Please check your username and password.” Moreover, I am not even able to access the interface where I could enter detailed server settings (IMAP/POP3, SMTP), port numbers, or security options—Thunderbird fails authentication before presenting any advanced configuration screens. This issue is an exception, as I have successfully added several other email accounts without any issues. I have verified the username and password—they work perfectly when I access the same account on my Android phone and in other email clients. Therefore, I believe the credentials are correct, and the issue seems specific to Thunderbird on Windows. Could you please assist me with the following: What steps can I take to access the settings interface for entering server details and ports? What default server (IMAP/POP3, SMTP) and port settings should Thunderbird automatically apply for the gurmanservis.cz domain? Are there any advanced security options (SSL/TLS, authentication methods) that might be blocking the login? Is there a known Thunderbird bug affecting authentication for this domain? Thank you in advance for your support. Best regards, Zdeněk Straka info@gurmanservis.cz