diff --git a/lib/pop3-connection.js b/lib/pop3-connection.js
index 361ce7af..be9facfd 100644
--- a/lib/pop3-connection.js
+++ b/lib/pop3-connection.js
@@ -171,15 +171,44 @@ class POP3Connection extends EventEmitter {
             return;
         }
         let line = this.queue.shift().trim();
+
+        if (typeof this._nextHandler === 'function') {
+            let handler = this._nextHandler;
+            this._nextHandler = null;
+            this._server.logger.debug({
+                tnx: 'receive',
+                cid: this._id,
+                user: this.session.user && this.session.user.username
+            }, 'C: <%s bytes of continue data>', Buffer.byteLength(line));
+            return handler(line, err => {
+                if (err) {
+                    this._server.logger.info({
+                        err,
+                        tnx: '+',
+                        cid: this._id,
+                        host: this.remoteAddress
+                    }, 'Error processing continue data. %s', err.message);
+                    this.send('-ERR ' + err.message);
+                    this.close();
+                } else {
+                    this.processQueue();
+                }
+            });
+        }
+
         let parts = line.split(' ');
         let command = parts.shift().toUpperCase();
         let args = parts.join(' ');
 
+        let logLine = (line || '').toString();
+        if (/^(PASS|AUTH PLAIN)\s+[^\s]+/i.test(line)) {
+            logLine = logLine.replace(/[^\s]+$/, '*hidden*');
+        }
         this._server.logger.debug({
             tnx: 'receive',
             cid: this._id,
             user: this.session.user && this.session.user.username
-        }, 'C:', (line || '').toString());
+        }, 'C:', logLine);
 
         if (typeof this['command_' + command] === 'function') {
             this['command_' + command](args, err => {
@@ -310,70 +339,26 @@ class POP3Connection extends EventEmitter {
 
         let params = args.split(/\s+/);
         let mechanism = params.shift().toUpperCase();
-        let plain = params.shift();
 
         if (mechanism !== 'PLAIN') {
             this.send('-ERR unsupported SASL mechanism');
             return next();
         }
 
-        if (params.length || !/^[a-zA-Z0-9+\/]+=+?$/.test(plain)) {
+        if (!params.length) {
+            this.send('+');
+            this._nextHandler = (args, next) => this.authPlain(args, next);
+            return next();
+        }
+
+        let plain = params.shift();
+
+        if (params.length) {
             this.send('-ERR malformed command');
             return next();
         }
 
-        let credentials = Buffer.from(plain, 'base64').toString().split('\x00');
-        if (credentials.length !== 3) {
-            this.send('-ERR malformed command');
-            return next();
-        }
-
-        let username = credentials[1] || credentials[0] || '';
-        let password = credentials[2] || '';
-
-        this._server.onAuth({
-            method: 'PLAIN',
-            username,
-            password
-        }, this.session, (err, response) => {
-
-            if (err) {
-                this._server.logger.info({
-                    err,
-                    tnx: 'autherror',
-                    cid: this._id,
-                    method: 'PLAIN',
-                    user: username
-                }, 'Authentication error for %s using %s. %s', username, 'PLAIN', err.message);
-                return next(err);
-            }
-
-            if (!response.user) {
-                this._server.logger.info({
-                    tnx: 'authfail',
-                    cid: this._id,
-                    method: 'PLAIN',
-                    user: username
-                }, 'Authentication failed for %s using %s', username, 'PLAIN');
-                this.send('-ERR [AUTH] ' + (response.message || 'Username and password not accepted'));
-                return next();
-            }
-
-            this._server.logger.info({
-                tnx: 'auth',
-                cid: this._id,
-                method: 'PLAIN',
-                user: username
-            }, '%s authenticated using %s', username, 'PLAIN');
-            this.session.user = response.user;
-
-            this.openMailbox(err => {
-                if (err) {
-                    return next(err);
-                }
-                next();
-            });
-        });
+        this.authPlain(plain, next);
     }
 
     // https://tools.ietf.org/html/rfc1939#page-9
@@ -662,7 +647,7 @@ class POP3Connection extends EventEmitter {
                                 } else {
                                     data = '';
                                 }
-                                this.write(Buffer.from(headers.replace(/^\./gm,'..'), 'binary'));
+                                this.write(Buffer.from(headers.replace(/^\./gm, '..'), 'binary'));
                             }
                         }
                         if (headers) {
@@ -682,7 +667,7 @@ class POP3Connection extends EventEmitter {
                                 } else {
                                     data = '';
                                 }
-                                this.write(Buffer.from(line.replace(/^\./gm,'..'), 'binary'));
+                                this.write(Buffer.from(line.replace(/^\./gm, '..'), 'binary'));
                                 if (linesSent >= lines) {
                                     finished = true;
                                     if (typeof stream.abort === 'function') {
@@ -705,6 +690,66 @@ class POP3Connection extends EventEmitter {
         });
     }
 
+    authPlain(plain, next) {
+        if (!/^[a-zA-Z0-9+\/]+=+?$/.test(plain)) {
+            this.send('-ERR malformed command');
+            return next();
+        }
+
+        let credentials = Buffer.from(plain, 'base64').toString().split('\x00');
+        if (credentials.length !== 3) {
+            this.send('-ERR malformed command');
+            return next();
+        }
+
+        let username = credentials[1] || credentials[0] || '';
+        let password = credentials[2] || '';
+
+        this._server.onAuth({
+            method: 'PLAIN',
+            username,
+            password
+        }, this.session, (err, response) => {
+
+            if (err) {
+                this._server.logger.info({
+                    err,
+                    tnx: 'autherror',
+                    cid: this._id,
+                    method: 'PLAIN',
+                    user: username
+                }, 'Authentication error for %s using %s. %s', username, 'PLAIN', err.message);
+                return next(err);
+            }
+
+            if (!response.user) {
+                this._server.logger.info({
+                    tnx: 'authfail',
+                    cid: this._id,
+                    method: 'PLAIN',
+                    user: username
+                }, 'Authentication failed for %s using %s', username, 'PLAIN');
+                this.send('-ERR [AUTH] ' + (response.message || 'Username and password not accepted'));
+                return next();
+            }
+
+            this._server.logger.info({
+                tnx: 'auth',
+                cid: this._id,
+                method: 'PLAIN',
+                user: username
+            }, '%s authenticated using %s', username, 'PLAIN');
+            this.session.user = response.user;
+
+            this.openMailbox(err => {
+                if (err) {
+                    return next(err);
+                }
+                next();
+            });
+        });
+    }
+
     openMailbox(next) {
         this._server.onListMessages(this.session, (err, listing) => {
             if (err) {