New user interface presents a much improved experience on both desktop and mobile. The theme is included in this release but is not yet default. It can be enabled in RC releases conveniently using the dropdown menu in the main navigation sidebar, next to 'Language'. (Note that public facing pages such as subscribe pages are unaffected.)
New theme switcher on the Config → Settings page allows the application theme to be set via the user interface for the first time
Security
Introduced Unique User ID code generation for all personalised links in campaigns
Increased entropy used by CSRF tokens used to authenticate links between admin pages
Introduced additional checks for user-submitted campaign data
Usability
Introduced Javascript-based loading of statistics for handling large datasets to avoid page load timeout errors on the following pages (See Commit 1 and 2):
Statistics overview
Domain Statistics
Campaign click statistics
View opens
View bounces per list
Fixed slow page load due to failed RSS News Feed caching. See the Pull Request.
Added accessibility labels to form fields on public subscribe pages. See the Pull Request.
Improved and compacted table layout of 'View members of list' page. See the Pull Request.
Improved About page formatting. See the Pull Request.
Added announcement mailing list signup form to about page. See the Pull Request.
Linked campaign title to view campaign on campaign statistics page. See the Pull Request.
Linked list name to List Members page from Subscriber Lists page. See the Pull Request.
Updated help page content, added links to resources. See the Pull Request.
Improved message queue processing notification email content. See the Pull Request.
Improved new installation email notification formatting. See the Pull Request.
Improved formatting of mail queue event log messages. See the Pull Request.
Improved formatting of Event log page. See Pull Request.
Improved date formatting on the Schedule tab of the Campaign composer pages. See the Pull Request.
Improved form field descriptions on Campaign composer page. See Pull Request.
Numerous fixes to table column titles and labels
Numerous number formatting fixes on Admin pages
Languages & Translations
Languages preferences are saved between sessions. When language is set manually it will be stored after logout (by default phpList uses the default language of the web browser)
Made 'Logout' and 'Login' buttons translatable in new theme See the Pull Request.
Numerous fixes to English language text capitalisation
Plugins
Introduced support for plugin handling of mail queue sending. See the Pull Request.
Other fixes
Fix bug misreporting bounce message download failure. See the Pull Request.
Made content of Database Check page translatable. See the Pull Request.