+++ This bug was initially created as a clone of Bug #861471 +++ Relevant Bugs: FX Bug 733632 - Remove TLS version UI (Options > Advanced > Encryption > Protocols) Core Bug 733642 - Allow the user to enable any version of TLS that libssl supports, maintaining our current defaults Bug 733642 Removed: > -pref("security.enable_ssl3", true); > -pref("security.enable_tls", true); Added: > +pref("security.tls.version.min", 0); > +pref("security.tls.version.max", 1); https://hg.mozilla.org/mozilla-central/rev/04dbe811e4a0#l3.26 > + // 0 means SSL 3.0, 1 means TLS 1.0, 2 means TLS 1.1, etc. From Bug 733632: > tl;dr: Let's remove the "Protocols" option in Advanced encryption options > dialog box. > > Right now, we have two checkboxes: > > [X] Use SSL 3.0 [X] Use TLS 1.0 > > We are adding support for TLS 1.1. When we add this support, we could add > another checkbox like this: > > [X] Use SSL 3.0 [X] Use TLS 1.0 [X] Use TLS 1.1 > > However, this would be confusing, because it is not possible to enable SSL 3.0 > and TLS 1.1 without also enabling TLS 1.0; the range of enabled versions must > be contiguous, so only the following choices would be valid: > > [X] Use SSL 3.0 [X] Use TLS 1.0 [X] Use TLS 1.1 > [X] Use SSL 3.0 [X] Use TLS 1.0 [ ] Use TLS 1.1 > [ ] Use SSL 3.0 [X] Use TLS 1.0 [X] Use TLS 1.1 > [X] Use SSL 3.0 [ ] Use TLS 1.0 [ ] Use TLS 1.1 > [ ] Use SSL 3.0 [X] Use TLS 1.0 [ ] Use TLS 1.1 > [ ] Use SSL 3.0 [ ] Use TLS 1.0 [X] Use TLS 1.1 > > Note also that the current UI lets us do this: > > [ ] Use SSL 3.0 [ ] Use TLS 1.0 > > which is nonsense, because at least one version must be enabled to do anything > sensible. > > We will have compatibility features implemented so that basically will really > need to toggle these prefs, except experts. Therefore, I think about:config is > a sufficient UI for controlling this feature. See Bug 733632 for other proposed UI.

Is this actually relevant for Lightning? I'm not using it myself, but I can't find the "Encryption" tab where the boxes are supposed to be provided. For SeaMonkey, bug 861471 provides the UI needed to modify those prefs, and they should be applicable to all protocols. Only Thunderbird would be affected as it doesn't provide any UI for the encryption protocols by itself.

Sunbird is currently scheduled to be removed from the comm-central tree leaving only those files relevant to Lightning. So I don't think this bug is useful/valid

Sunbird code was removed from tree, bug is no longer required.