How Mailchimp/Mailgun does to sign mail twice

i use OpenDKIM and Postfix. I am trying to sign the mail like mail chimp does with opendkim.

Here an example:

   dkim=pass header.i=@veromailer.com header.s=krs header.b=Bahk1U6e;   dkim=pass header.i=@mailgun.org header.s=mg header.b=UUj68MYJ;   spf=pass (google.com: domain of bounce+4f9fc5.a3809-emawata=gmail.com@veromailer.com designates 69.72.47.114 as 

They sign the mail twice.

Here my config on opendkim

KeyTablemail._domainkey.compraesta.tk compraesta.tk:mail:/etc/opendkim/keys/compraesta.tk/mail.privatemail._domainkey.mail01.devpmta.tk mail01.devpmta.tk:mail:/etc/opendkim/keys/mail01.devpmta.tk/mail.privateSigningTable*@compraesta.tk mail._domainkey.compraesta.tk*@mail01.devpmta.tk mail._domainkey.mail01.devpmta.tkopendkim.confPidFile /var/run/opendkim/opendkim.pidMode    svSyslog  yesSyslogSuccess   yesLogWhy  yesUserID  opendkim:opendkimSocket  inet:8891@localhostUmask   002SendReports     yesSoftwareHeader  yesCanonicalization        relaxed/relaxedMinimumKeyBits  1024KeyFile /etc/opendkim/keys/default.privateKeyTable        /etc/opendkim/KeyTableSigningTable    refile:/etc/opendkim/SigningTableExternalIgnoreList      refile:/etc/opendkim/TrustedHostsInternalHosts   refile:/etc/opendkim/TrustedHosts

I can only make the signature in the header from but not in the mail from.

Any ideas?

Regards,