Add DKIM signing

examples/dkim.js

@@ -0,0 +1,19 @@
+var fs = require('fs');
+var sendmail = require('../sendmail')({
+  silent:true,
+  dkim: {
+    privateKey: fs.readFileSync('dkim-private.pem', 'utf-8'),
+    keySelector: 'mydomainkey'
+  }
+});
+
+sendmail({
+    from: 'test@yourdomain.com',
+    to: 'info@yourdomain.com',
+    replyTo: 'jason@yourdomain.com',
+    subject: 'MailComposer sendmail',
+    html: 'Mail of test sendmail ',
+  }, function(err, reply) {
+    console.log(err && err.stack);
+    console.dir(reply);
+});

package.json

@@ -12,6 +12,7 @@
     "node": ">=0.6.0"
   },
   "dependencies": {
+    "dkim-signer": "^0.2.2",
     "mailcomposer": "^3.10.0"
   },
   "devDependencies": {

sendmail.js

@@ -1,5 +1,6 @@
 var tcp = require('net');
 var dns = require('dns');
+var DKIMSign = require('dkim-signer').DKIMSign;
 var CRLF = '\r\n';
 
 function dummy(){}
@@ -16,6 +17,8 @@ var exports = module.exports = function(options) {
     warn: console.warn,
     error: console.error
   })
+  var dkimPrivateKey = (options.dkim || {}).privateKey
+  var dkimKeySelector = (options.dkim || {}).keySelector || 'dkim'
 
   /*
    *   邮件服务返回代码含义 Mail service return code Meaning
@@ -275,10 +278,18 @@ var exports = module.exports = function(options) {
         callback(err, null);
         return;
       }
+      if (dkimPrivateKey) {
+        var signature = DKIMSign(message, {
+            privateKey: dkimPrivateKey,
+            keySelector: dkimKeySelector,
+            domainName: srcHost
+        });
+        message = signature + '\r\n' + message;
+      }
       for (var domain in groups) {
         sendToSMTP(domain, srcHost, from, groups[domain], message, callback);
       }
-    })   
+    })
     // COMMENTED OUT BY GP BECAUSE I SAW NO USE FOR IT
     // var domainsCount = Object.keys(groups).length
     // var doneCount