add vista integration string before the l10n freeze

mail/locales/en-US/installer/custom.properties

@@ -46,6 +46,7 @@
 # You can use \n to create a newline in the string but only when the string
 # from en-US contains a \n.
 
+REG_APP_DESC=${BrandShortName} is a full-featured email application. ${BrandShortName} supports IMAP and POP mail protocols, as well as HTML mail formatting. Built-in junk mail controls, RSS capabilities, powerful quick search, spell check as you type, global inbox, and advanced message filtering round out ${BrandShortName}'s modern feature set.
 OPTIONAL_COMPONENTS_TITLE=Choose Optional Components
 OPTIONAL_COMPONENTS_SUBTITLE=Choose which features of $(^NameDA) you want to install.
 OPTIONAL_COMPONENTS_LABEL=Optional Components: