PROBLEM SMTP SERVER
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 redacted@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
(PII removed by moderator)
Modified by Ed
All Replies (4)
Thunderbird has no authority or access to the SMTP server to which you refer. All Thunderbird does is send your message to that server for processing. Possibly, if you post a screenshot of the SMTP server settings pane and one of the 'server settings' pane, some suggestions may come forth. thank you.
Set the authentication method to OAuth2 and enter the account (not app) password in the OAuth2 window when asked to allow access. Set OAuth2 on the incoming outlook.office365.com as well.
Thank you for your reply. Here are the technical settings currently used for this account: 1. Incoming Server (IMAP): Server: outlook.office365.com | Port: 993 | SSL/TLS Authentication: Normal Password (using a 16-character App Password) Status: Working perfectly. 2. Outgoing Server (SMTP): Server: smtp.office365.com | Port: 587 | STARTTLS Authentication: Normal Password (using the same 16-character App Password) User Name: Full email address (josettethirion@outlook.be) Status: Fails with "Command Error 12". 3. Context: Two-Step Verification is active on the Microsoft account. Other Outlook accounts with identical settings on the same Thunderbird client are working fine. The issue is strictly limited to the SMTP connection for this specific account. If the settings are identical to my working accounts, why does the server reject the connection specifically for this one? Could this be a cached credential issue within Thunderbird’s internal database that a simple password purge wouldn't fix?
When there are multiple accounts on the same service, some working, some not, the first thing I'd check is whether the accounts are all aligned with the correct smtp servers, as described in this topic:
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