SeaMonkey 2.49.4 contains (among other changes) the following major changes relative to SeaMonkey 2.49.3:
SeaMonkey 2.49.4 uses the same backend as Firefox and contains the relevant Firefox 52.9.0 ESR security fixes.
SeaMonkey 2.49.4 shares most parts of the mail and news code with Thunderbird. Please read the Thunderbird 52.9.1 release notes for specific changes and security fixes in this release.
https://www.seamonkey-project.org/releases/seamonkey2.49.4/#new
SeaMonkey 2.49.4 contains (among other changes) the following major changes relative to SeaMonkey 2.49.3:
SeaMonkey 2.49.4 uses the same backend as Firefox and contains the relevant Firefox 52.9.0 ESR security fixes.
SeaMonkey 2.49.4 shares most parts of the mail and news code with Thunderbird. Please read the Thunderbird 52.9.1 release notes for specific changes and security fixes in this release.