Custom Python 3 Milter on Zimbra10

[Rio Dang]

I am using zimbra10 and using the Custom Python 3 Milter on Zimbra10 feature to make banners and I am having difficulty in the following:
I am having a problem that emails that are not in the whitelist will have a dkim fail error because I added the banner, and the email will go to the junk folder
Inbound: any body modify ? DKIM fail (cannot be fixed)
Has anyone done this and has any solution for this problem