Don't close the VERP Server on error. And improved error reporting.

Based on https://git.io/vQLS7 , I believe the change introduced in
https://git.io/vQL7u "server.close()" to be in error, and intended to
close one connection, like it’s handled in https://git.io/vQLSF

Perhaps SMTPServer isn't even meant to throw ECONNRESET and EPIPE in
the first place.

services/postfix-bounce-server.js

@@ -70,17 +70,37 @@ let server = net.createServer(socket => {
     });
 });
 
-server.on('error', err => {
-    log.error('POSTFIXBOUNCE', err && err.stack);
-});
-
 module.exports = callback => {
-    if (config.postfixbounce.enabled) {
+    if (!config.postfixbounce.enabled) {
-        server.listen(config.postfixbounce.port, config.postfixbounce.host, () => {
+        return setImmediate(callback);
-            log.info('POSTFIXBOUNCE', 'Server listening on port %s', config.postfixbounce.port);
-            setImmediate(callback);
-        });
-    } else {
-        setImmediate(callback);
     }
+
+    let started = false;
+
+    server.on('error', err => {
+        const port = config.postfixbounce.port;
+        const bind = typeof port === 'string' ? 'Pipe ' + port : 'Port ' + port;
+
+        switch (err.code) {
+            case 'EACCES':
+                log.error('POSTFIXBOUNCE', '%s requires elevated privileges.', bind);
+                break;
+            case 'EADDRINUSE':
+                log.error('POSTFIXBOUNCE', '%s is already in use', bind);
+                break;
+            default:
+                log.error('POSTFIXBOUNCE', err);
+        }
+
+        if (!started) {
+            started = true;
+            return callback(err);
+        }
+    });
+
+    server.listen(config.postfixbounce.port, config.postfixbounce.host, () => {
+        started = true;
+        log.info('POSTFIXBOUNCE', 'Server listening on port %s', config.postfixbounce.port);
+        setImmediate(callback);
+    });
 };

services/test-server.js

@@ -164,6 +164,10 @@ let mailBoxServer = http.createServer((req, res) => {
     });
 });
 
+mailBoxServer.on('error', err => {
+    log.error('Test SMTP Mailbox Server', err);
+});
+
 module.exports = callback => {
     if (config.testserver.enabled) {
         server.listen(config.testserver.port, config.testserver.host, () => {

services/verp-server.js

@@ -99,15 +99,36 @@ let server = new SMTPServer({
     }
 });
 
-server.on('error', err => {
-    log.error('VERP', err);
-    server.close();
-});
-
 module.exports = callback => {
     if (!config.verp.enabled) {
         return setImmediate(callback);
     }
+
+    let started = false;
+
+    server.on('error', err => {
+        const port = config.verp.port;
+        const bind = typeof port === 'string' ? 'Pipe ' + port : 'Port ' + port;
+
+        switch (err.code) {
+            case 'EACCES':
+                log.error('VERP', '%s requires elevated privileges', bind);
+                break;
+            case 'EADDRINUSE':
+                log.error('VERP', '%s is already in use', bind);
+                break;
+            case 'ECONNRESET': // Usually happens when a client does not disconnect cleanly
+            case 'EPIPE': // Remote connection was closed before the server attempted to send data
+            default:
+                log.error('VERP', err);
+        }
+
+        if (!started) {
+            started = true;
+            return callback(err);
+        }
+    });
+
     let hosts;
     if (typeof config.verp.host === 'string' && config.verp.host) {
         hosts = config.verp.host.trim().split(',').map(host => host.trim()).filter(host => host.trim());
@@ -121,6 +142,7 @@ module.exports = callback => {
     let pos = 0;
     let startNextHost = () => {
         if (pos >= hosts.length) {
+            started = true;
             return setImmediate(callback);
         }
         let host = hosts[pos++];