[GoodThings2Life]

Install the attached cab and you can use the Menu > Mark All As Read option.

Although it doesn't give you the option directly from TouchFLO, at least you can open the Inbox and then do it fairly easily.

I'm wondering however, if you're interested in testing it out, that perhaps you could do this:

[HKEY_CURRENT_USER\Software\HTC\BootLauncher\Servic es\OutlookEnhancement], set Module to \\windows\\InboxMenuExtensibility.dll

That might allow the Reply All left softkey to become Mark All as Read... or not.