Fix Outlook Error 0x8004210B
When sending email with Outlook 2002, 2003 or 2007, the error code 0x8004210B may appear. The full message is usually:
Task ‘Sending juanperez@example.com ’ reported error (0x8004210B): The operation has timed out waiting for a response from the sending server (SMTP). If you continue to receive this message, contact your server administrator or Internet Service Provider (ISP).
Common causes and solutions
1. SMTP port without SSL marked
If you configured port 465 (the encrypted port) but forgot to check the SSL option, you will get this error. Enable SSL encryption on port 465 from the account settings in Outlook.
2. TLS selected instead of SSL
In Outlook 2007 and 2010, if you choose TLS as the outgoing server encryption and set the port to 465, it also fails. In Outlook, “TLS” actually means STARTTLS, which operates on another unencrypted port. Solution: Change the option to SSL.
3. Incorrect server names
Verify that the incoming and outgoing servers have the correct names and match each other.
4. Antivirus interfering
Some antiviruses cause this error. Temporarily disable the antivirus and test sending. If it works by disabling it, specifically disable scanning of incoming and outgoing mail.
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