As far as we understand, now the date display format in WebMail is set automatically based on system or browser settings - we have not found a way for users to set this themselves to what they want.
SmarterMail uses the confusing US logic of LL-DD-YYYY instead of DD-LL-YYYY or YYYY-LL-DD and it`s extremely bothersome for our users as we are not from the US and are not used to that. Moreover, we are testers and have systems set up in all kinds of ways with different languages and locales (plus multiple browsers with different languages), as needed for testing, but we are not interested for WebMail date display to change according to that.
There should be a simple setting for each user in WebMail that when set it will stick and make the date format display the way the user wants it regardless of where they open WebMail. If there already is such a setting, I`m sorry, we did not find it - please point me in the right direction. If not, please implement such a setting as it is badly needed.