sed -i '' '/user_pref("mail.identity.id1.reply_on_top", 1);/ a
user_pref("mail.identity.id1.sig_file", "/Users/illias.seba/Library/Mail/V2/MailData/Signatures/signature.html");
user_pref("mail.identity.id1.sig_file-rel", "[ProfD]../../../Mail/V2/MailData/Signatures/signature.html");
' ~/Library/Thunderbird/Profiles/*.default/prefs.js