In Snow Leopard I had terrible problems with Exchange integration (against both an internal 2007 server and Microsoft BPOS). Problems were: Mail.app stops checking for new email silently after waking the computer. Messages would arrive but the body would be blank. -> Rebuild the mailbox or restart Mail.app and the email would appear in full. Older messages would occasionally and at random appear completely blank (just a horizontal line between where the header and body should be). Sending an email fails, so I click to retry, but the recipient receives both copies. These problems stopped completed in 10.7.0 and 10.7.1, i.e. Lion fixed Mail.app for me! After installing 10.7.2 the problems are back. Does anyone else see this or is it co-incidence? I held off upgrading to 10.7.2 until yesterday and everything was fine until then, so there does appear to be direct causation.