Custom form icon issue

[Bingo]

I'm using a custom form with certain hidden fields. I
set the Large Icon and Small Icon properties to the
closed yellow envelop icon. The problem is that even the
emails have been read, in Outlook, the icon stays as the
closed yellow envelop icon instead of the open white
envelop icon. How do I make sure all the emails using
this custom form will use the same icons like typic
Outlook emails? Thanks.

 

[Sue Mosher [MVP-Outlook]]

You can't. Custom forms don't have dual open/closed icons.