You are aware that cross posting is considered very bad form in the NNTP world I assume. If you do cross post I strongly urge you to set the followups to for the post to a single newsgroup. they at least any flame war will be limited to the single group. In Thunderbird select your newsroup to post to, click write and the first group will be auto entered. Then select the next line of addresses, select newsgroup instead of To and start typing the newsgroup name and select from the drop down list.