DKIM or DomainKeys Identified Mail is an email authentication method that tries to identify email spoofing attempts (creation of email messages with a forged sender address). DKIM enables you as the receiver of the email to verify that an email claiming to be from a specific domain is actually authorized by the owner of that domain. It is done with the help of a digital signature, tied to a domain name, for each sent email. This can be verified by looking up the sender’s public key published in the DNS.
In Zimbra, DKIM can be used both to check incoming emails and to sign outgoing emails. This guide shows you how to configure Zimbra to check incoming emails using DKIM.
How to Configure DKIM for Checking Incoming Emails
By configuring DKIM for checking incoming emails, you can reject incoming emails with no DKIM record. In this section, we configure the OpenDKIM to check incoming emails.
1. Open OpenDKIM configuration file
su - zimbra vi /opt/zimbra/conf/opendkim.conf.in
2. Set these configurations, save and exit
On-NoSignature reject Mode sv
3. Restart OpenDKIM
Set these configurations, save and exit.