Hello. This is my first post, so my apologies if it is in the wrong thread. I am running ISPConfig version 3.1.6 on a CentOS version 7.4.1708 I enabled DKIM signing on one of my mail domains. I see the keys, private and public, and the DKIM DNS TXT entry is there and available. So everything looks good to me. When I send an email, there is no DKIM entry in the headers. Looking at the maillog, I could see the error, which is the title of this post. dkim: not signing, empty signing domain. (Note: the above error does show the email domain.) When I run amavisd showkeys, I receive the following. No DKIM private keys declared in a config file. If you have any information regarding this type of issue, please post a comment and let me know. Thanks.