I'm not sure if that's the proper way to solve the problem, but it seems to work for me. Additionallly to the aforementioned fix, i added the last line to the following stanza:
'Reply address
Dim mailboxReplyTo As String
mailboxReplyTo = colorProfile.GetItemValue("MailboxReplyTo")(eMailAddressNo)
Call note.ReplaceItemValue( "ReplyTo", mailboxReplyTo )
Call note.ReplaceItemValue( "$InetPrincipal", mailboxReplyTo )
mailboxReplyTo = GetMessagePrincipalName( colorProfile,eMailAddressNo) + " <" + mailboxreplyto + ">"
I've to mention that i'm currently using a german version of the template which was customized a bit further. It allows you to specify multiple from-addresses to choose from when you send a mail. In the original template, it would look like this:
'Reply address
Dim mailboxReplyTo As String
mailboxReplyTo = colorProfile.GetItemValue("MailboxReplyTo")(0)
Call note.ReplaceItemValue( "ReplyTo", mailboxReplyTo )
Call note.ReplaceItemValue( "$InetPrincipal", mailboxReplyTo )
mailboxReplyTo = GetMessagePrincipalName( colorProfile,eMailAddressNo) + " <" + mailboxreplyto + ">"
Don't forget to add the following line to the end of the section titled "Mail router needs a special field, named Recipients" as mentioned before:
Call note.ReplaceItemValue ("Principal", note.from)