Hi and thank you for your attention.
I want to create an extension for Mozilla Thunderbird that implement some sort of black list. It is possible to create filter rules for mails and I want to add a button which create filter rule for selected mail. These rules are stored in msgFilterRules.dat file and I could manually edit it but only when Thunderbird is closed.
Is there any way to manipulate this file with some sort of API or WebExtensions?