User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.0.3) Gecko/2008092417 Firefox/3.0.3 Build Identifier: version 2.0.0.17 (20080914) Thunderbird does not allow me to mix AND and OR when designing a filter. I have the desire to create a filter that works along the lines of Subject: String AND (From: email OR From: email) Under current setup, this cannot be achieved. I attempted to edit my message filters directly from the file, but it does not appear to work. Reproducible: Always Steps to Reproduce: Attempt to create a filter that requires a mix of required and optional conditions Actual Results: Cannot mix AND and OR. Message filter matching is either ALL or AT LEAST ONE of the following conditions. Expected Results: Create a filter that allows me to filter on a certain subject and one of two possible source emails. Not sure if this should be handled as a bug or an enhancement. I find it to be quite annoying, but I doubt a large number of users get dinged by this. I happen to have rather complicated filtering needs that may exceed the average user.