This applies to Nodemailer v1.0+. Older versions have DKIM support built in.

Install from npm

npm install nodemailer-dkim --save

Load the signer function

var signer = require('nodemailer-dkim').signer;

Attach it as a 'stream' handler for a nodemailer transport object

transporter.use('stream', signer(options))

Where

• options is the DKIM options object
  • domainName is the domain name that is being used for signing
  • keySelector is the key selector (if you have set up a TXT record with DKIM public key at zzz._domainkey.blurdybloop.com then zzz is the selector)
  • privateKey is the private key that is used for DKIM signing (string)
  • headerFieldNames is an (optional) colon separated list of header fields to sign, by default all fields suggested by RFC4871 #5.5 are used

All messages transmitted through this transport objects are from now on DKIM signed.

NB! If several header fields with the same name exists, only the last one (the one in the bottom) is signed.

var nodemailer = require('nodemailer');
var transporter = nodemailer.createTransport();
transporter.use('stream', require('nodemailer-dkim').signer({
    domainName: 'kreata.ee',
    keySelector: 'test',
    privateKey: fs.readFileSync('private.pem')
}));
transporter.sendMail({
    from: 'sender@address',
    to: 'receiver@address',
    subject: 'hello',
    text: 'hello world!'
}, function(err, response) {
    console.log(err || response);
});

You can use this module to check if your configuration is correct and the private key matches the public key listed in DNS

var verifyKeys = require('nodemailer-dkim').verifyKeys;
verifyKeys(options, callback);

Where

• options is the same option object you use for the signer function
• callback is the callback to run once verification is completed

Example

verifyKeys({
    domainName: 'kreata.ee',
    keySelector: 'test',
    privateKey: fs.readFileSync('private.pem')
}, function(err, success){
    if(err){
        console.log('Verification failed');
        console.log(err);
    }else if(success){
        console.log('Verification successful, keys match');
    }
});

MIT