A new plugin lets you immediately verify the sender by comparing the From: line and sending IP of emails against the published Sender Policy Framework (SPF) and DNS-based reputation lists. Verifying addresses may prevent you from phishing attacks which is not such a bad idea.

BTW if you want to add the date in the reply header just change
\Programme\Mozilla Thunderbird\defaults\pref\mailnews.js from

pref(“mailnews.reply_header_type”, 1);

to

pref(“mailnews.reply_header_type”, 2);