Add possibility to have multiple Internet email addresses assigned to a mail-in database

Now it is only possible to define 1 Internet email address to a mail-in database document in the Directory. The mail12.ntf template makes it possible to use the sender address to be chosen through access & delegation preferences. But now this is limited to the user or the single assigned mail-in Internet email address.

Even when you create multiple mail-in documents pointing to the same mail-in database and each have there own Internet email address assigned. The mail template does only provide the first found Internet email address of these mail-in documents as selection to set the sender address.

I would like to see the possibility to add multiple Internet email adresses to one mail-in document. Like in person document this is possible through adding the additional address to the field UserName or ShortName. And the mail template must provide the selection to set the sender address, the same way it is handled with the person documents.