This feature is not available in LISTSERV Lite.

In order for DKIM support to work, we assume that DKIM support has already been configured in DNS for the domains you will be signing for, per the DomainKeys Identified Mail documentation.  If not, general instructions are provided below.

DKIM support is available for LISTSERV Classic and HPO, on all operating systems except for z/VM. It is not available in LISTSERV Lite.

Important: Support for DKIM replaced support for the old Yahoo DomainKeys system, which is now deprecated, beginning with LISTSERV 16.0-2017a.

Most LISTSERV sites already using DomainKeys authentication will find this to be a transparent change when upgrading from an earlier version, with no need to make any adjustment to your current settings.  However, see below.

Important: Sites running older versions of LISTSERV which supported the Yahoo DomainKeys specification will wish to review their existing key pair before upgrading to LISTSERV 16.0-2017a or later, as key lengths which were sufficient for DomainKeys may be too short for DKIM. Per RFC 6376 “DomainKeys Identified Mail (DKIM) Signatures”, Section 3.3.3, “Signers MUST use RSA keys of at least 1024 bits for long-lived keys”, whereas many DomainKeys sites may be using keys of 512 or 768 bits.

In addition, RFC 8301 updates RFC 6376 and states in Section 3.1 that “DKIM supports multiple digital signature algorithms.  Two algorithms are defined by this specification at this time: rsa-sha1 and rsa-sha256.  Signers MUST sign using rsa-sha256.  Verifiers MUST be able to verify using rsa-sha256.  rsa-sha1 MUST NOT be used for signing or verifying.”

Bottom line:  L-Soft strongly recommends that all DKIM keys MUST be 1024 bits or more, and they MUST be SHA-256 (AKA SHA-2) keys.  Keys created with the SHA-1 algorithm are NOT supported by the DKIM specification, and MUST NOT be used.  Key pairs NOT meeting these specifications are used strictly at your own risk.


12.1 Creating DKIM keys and configuring DNS

12.2 Creating DNS records for DKIM

12.3 LISTSERV configuration

12.4 Starting LISTSERV with DKIM support

12.5 Using DKIM with LISTSERV

12.6 Restrictions and implementation choices

12.7 Testing DKIM