*Microsoft Security Essentials aka MSE (Settings | Excluded Files & Folders | add \users\xxxx\appdata\roaming\thunderbird) [http://groups.google.com/group/mozilla.support.thunderbird/browse_thread/thread/93ab6d849bd87918] [http://groups.google.com/group/mozilla.support.thunderbird/browse_thread/thread/84767c1397f8d560/d2ec367b9d781522?lnk=raot] {{Bug|621083}}
*pctools internet security 2011 {{bug|610106}}
*Secunia PSI [http://gsfn.us/t/oqje] (User Contributed Notes) - ** as of January 11, 2012,by default Secunia PS 2.0 forces an update to English rather than localized Thunderbird (; '''WORKAROUND from secunia''': "To change this, the user can double-click the program entry in the Scan Results and then choose the preferred language in the drop-down menu. We are aware that this approach may not be the most intuitive for our users and we are currently treating it as a bug. I have taken the freedom to quote your email to "bump up" our bug report and I have also raised the severity of the bug."
*Sophos - Instructions for [http://www.sophos.com/support/knowledgebase/article/25760.html Sophos] (untested)
* Spamfighter - due to a possible bug in Spamfighter (like Kaspersky it's not following the rules for Thunderbird add-ons), [http://community.spamfighter.com/forums/p/237/888.aspx after each 3.1 upgrade you have to repair it or reinstall it]; [http://getsatisfaction.com/mozilla_messaging/topics/cant_send_emails_since_3_1_5_was_visited_upon_me GS1], [http://getsatisfaction.com/mozilla_messaging/topics/i_updated_to_3_1_5_now_cant_send_messages_i_push_the_send_button_and_nothing_happens#reply_3777701 GS2] (see Spamfighter solution below)