I'm using Mozilla-Thunderbird with my MS Exchange IMAP server at work. When I send an email to the Internet, my Postfix MTA gives the following message: forged name in Message-ID: header: and rejects the email. I've successfully sent email from Kmail by changing the Message-ID Suffix in the Composing settings but I can't find a similar setting with Thunderbird. Any ideas? Maybe found in about:config?