If you are using the Hostpack SMTP server « outgoing.hostpack.lu » you can benefit from automatic DKIM signing of your messages by simply adding the following DNS records to your domain:

hostpack1._domainkey.yourdomain.name. CNAME hostpack1._domainkey.hostpack.lu.
hostpack2._domainkey.yourdomain.name. CNAME hostpack2._domainkey.hostpack.lu.

Doing so, your mail will be signed with the POST managed DKIM keys for the Hostpack platform, in the name of your domain.