User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8.1.13) Gecko/20080313 SeaMonkey/1.1.9 Build Identifier: Thunderbird 2.0.0.12 (20080213) RFC 3676 (Section 4.3) describes the convention that signatures in NNTP (newsgroup) messages be preceded with a line containing "-- " (dash-dash-space). This RFC does not apply to E-mail at all. No RFC or Internet standard can be found that describes such a convention for E-mail messages. Thus, this feature should be optional for Thunderbird accounts that are for E-mail but remain mandatory for accounts that are for NNTP. Reproducible: Always Steps to Reproduce: 1. 2. 3. See the <news://news.mozilla.org:119/mozilla.support.thunderbird> thread with the subject "Signatures and "Double Dashes". The original message in that thread was from someone wanting to deploy Thunderbird across a company and apparently is encountering resistance from customers who are not familiar with the delimiter. Thus, by not making this optional, a potential expansion of the Thunderbird customer base is impaired. Also, RFC 3676 is in conflict with RFC 4480. If you try to place your PGP signature in the signature area of a message, the dash-dash-space becomes dash-space-dash-dash-space per Section 7.1 of RFC 4880. That is, the -- before your signature becomes - -- If you remove the beginning dash-space, you alter the message after it was signed and thus invalidate the signature. If you leave the dash-space, the dash-dash-space NNTP signature indicator described in Section 4.3 of RFC 3676 is invalidated.