opendkim-testmsg(8)

NAME
opendkim-testmsg - DKIM message test tool

SYNOPSIS
opendkim-testmsg [-C] [-d domain] [-K] [-k keypath] [-s selector] [-t path]

DESCRIPTION
opendkim-testmsg signs or verifies an input message. This is similar to the test mode for opendkim(8) except that it does not use the same configuration system or milter interface. Rather, it is a direct access to the DKIM library with those functions out of the way. The message is read from standard input. In signing mode, the complete signed message will then be written to standard output. When verifying, there will be no output unless an error occurred. To sign a message, the -d, -k and -s options must all be provided. If all of them are absent, the input message will be verified. If some but not all are present, an error is returned. Both RSA and Ed25519 private keys are supported.

OPTIONS

-C  If specified, the signature header field generated in signing mode will be line-terminated with carriage-return line-feed, instead of just line-feed.

-d domain
    Names the domain in which signing is to be done. More specifically, names the domain in which the public key matching the provided private key would be found in a live test.

-K  Arranges to keep temporary files generated during message canonicalization for debugging purposes.

-k keypath
    Specifies the path to the private key file which should be used to sign the input message.

-s selector
    Names the selector within the specified domain that should be included in the signature.

-t path
    Specifies the directory in which temporary files are to be created. The default is /tmp.

VERSION
This man page covers the version of opendkim-testmsg that shipped with version 3.0.0 of OpenDKIM.

COPYRIGHT
Copyright (c) 2009-2015, The Trusted Domain Project.
Copyright (c) 2026, PhoenixDKIM contributors.
All rights reserved.

SEE ALSO
opendkim(8), opendkim-genkey(8), opendkim-testkey(8)

RFC 6376 - DomainKeys Identified Mail

RFC 8463 - A New Cryptographic Signature Method for DomainKeys Identified Mail (Ed25519)