This doesn't quite make sense to me... just upgraded to 6.0.5, and someone pointed out that right-clicking an email received and selecting "Search" would usually perform a search for all messages from that email address. But now, it returns no results. So say I right-click a message from email@example.com, it puts "from:(firstname.lastname@example.org)" in the search bar, but with no results shown. If I throw in a trailing asterisk... "from:(email@example.com*)"... then I am correctly shown the results.
Is this a 6.0.5 bug? Just upgraded from 5.0.x series yesterday, so looking from some confirmation from someone before I file a bugzilla entry.