Subject: Persistent SMTP block on specific Outlook account (IMAP functional) ​Problem Description: Systematic failure of outgoing emails via SMTP on Mozilla Thunderbird for the address josettethirion@outlook.be. Crucial Note: Incoming mail (IMAP) works perfectly with the same credentials, proving that the authentication and the password used are correct. ​Technical Data & Actions Taken: ​SMTP Configuration: Server smtp.office365.com, Port 587, STARTTLS (or port 465 SSL/TLS). ​Authentication: Using a 16-character App Password generated after enabling Two-Step Verification. ​Symptom: Systematic rejection of the SMTP connection (Command Error 12 or timeout). Other Outlook accounts configured on the same Thunderbird client and the same internet connection (Belgium) are working without any issues. ​Tests Performed: Complete purge of Thunderbird's password manager, alias verification, and full restart of network equipment. ​Conclusion: Since the reception service is operational and full access is functional via Webmail/Outlook App, the block is specific to the SMTP protocol for this particular account on the Microsoft server side. ​Request: Please lift any security restrictions or reset security flags for the SMTP service on this specific account. My mail for respons : [edited from public community support forum] @gmail.com