The new version starts faster, performs better and includes many improvements in various areas of the program.
The developers have come up with a bunch of improvements aimed at boosting the performance of the program. It starts even quicker now, the internal image viewer takes much less time to display large images, IMAP4 and MAPI accounts fetch messages at a higher speed. Replying to HTML messages with missing external images is speedy again. Other features of the program are also working faster.
There are other important improvements as well: address books synchronize with iCloud, print preview works properly, interface optimization for high resolution monitors and many more. Please refer to the entire list of changes.