This update for Mozilla Thunderbird to version 45.4.0 fixes the following issues:

- When using Thunderbird in a browser like context, for rendering HTML e-mail or feeds,
  it may be affected by vulnerabilities also fixed in Firefox ESR 45.4. (MFSA 2016-86, boo#999701)

The following bugs were fixed in this release:

- Display name was truncated if no separating space before email address
- Recipient addresses were shown in wrong color in some circumstances
- Additional spaces were inserted when drafts were edited.
- Mail saved as template copied In-Reply-To and References from original email.
- Threading broken when editing message draft, due to loss of Message-ID
- "Apply columns to..." did not honor special folders