501 Command "HELO" requires an argument問(wèn)題的解決方法

更新時(shí)間：2013年08月30日 09:07:30 作者：

換一個(gè)windows服務(wù)器，發(fā)現(xiàn)就沒(méi)這樣的問(wèn)題，僅在一臺(tái)Linux服務(wù)器上可以重現(xiàn)，直觀感覺(jué)就是這臺(tái)Linux服務(wù)器某些配置有問(wèn)題

場(chǎng)景描述：
保存郵箱配置時(shí)自動(dòng)探測(cè)郵箱配置參數(shù)是否正確，結(jié)果發(fā)現(xiàn)在探測(cè)SMTP時(shí)，系統(tǒng)報(bào)出如下異常：

復(fù)制代碼代碼如下:

javax.mail.MessagingException: 501 Command "HELO" requires an argument
        at com.sun.mail.smtp.SMTPTransport.issueCommand(SMTPTransport.java:1363)
        at com.sun.mail.smtp.SMTPTransport.helo(SMTPTransport.java:838)
        at com.sun.mail.smtp.SMTPTransport.protocolConnect(SMTPTransport.java:375)
        at javax.mail.Service.connect(Service.java:275)

但是換一個(gè)windows服務(wù)器，發(fā)現(xiàn)就沒(méi)這樣的問(wèn)題，僅在一臺(tái)Linux服務(wù)器上可以重現(xiàn)，直觀感覺(jué)就是這臺(tái)Linux服務(wù)器某些配置有問(wèn)題。

排查步驟
1. 找一臺(tái)同樣操作系統(tǒng)的Linux服務(wù)器，驗(yàn)證郵箱配置，ok，排除Linux操作系統(tǒng)特殊性的問(wèn)題
2. 直接在Linux服務(wù)器上使用telnet連接對(duì)端郵件服務(wù)器的SMTP端口，OK，排除該服務(wù)器的網(wǎng)絡(luò)問(wèn)題
3. 查找HELO指令解釋

復(fù)制代碼代碼如下:

HELO
-- Initiates a conversation with the mail server. When using this command you can specify your domain name so that the mail server knows who you are. For example, HELO mailhost2. cf.ac.uk.

發(fā)現(xiàn)HELO指令后面需要跟一個(gè)發(fā)起者的主機(jī)名，告訴SMTP服務(wù)器這個(gè)消息來(lái)源是哪里。
再看異常信息是"501 Command "HELO" requires an argument"，很明顯，程序在跟SMTP SERVER交互過(guò)程中沒(méi)有傳遞源主機(jī)域名。

4. 查看JAVA MAIL源碼
查找HELO指令，如下：

復(fù)制代碼代碼如下:

        /**
         * Issue the <code>HELO</code> command.
         * 
         * @param domain
         *            our domain
         * 
         * @since JavaMail 1.4.1
         */
        protected void helo(String domain) throws MessagingException {
                if (domain != null)
                        issueCommand("HELO " + domain, 250);
                else
                        issueCommand("HELO", 250);
        }

查找helo方法在哪里被調(diào)用，看看domain如何被傳遞過(guò)來(lái)的

復(fù)制代碼代碼如下:

                if (useEhlo)
                        succeed = ehlo(getLocalHost());
                if (!succeed)
                        helo(getLocalHost());

順理成章，接著找getLocalHost()方法，定義如下：

復(fù)制代碼代碼如下:

        /**
         * Get the name of the local host, for use in the EHLO and HELO commands.
         * The property mail.smtp.localhost overrides mail.smtp.localaddress, which
         * overrides what InetAddress would tell us.
         */
        public synchronized String getLocalHost() {
                try {
                        // get our hostname and cache it for future use
                        if (localHostName == null || localHostName.length() <= 0)
                                localHostName = session.getProperty("mail." + name + ".localhost");
                        if (localHostName == null || localHostName.length() <= 0)
                                localHostName = session.getProperty("mail." + name+ ".localaddress");
                        if (localHostName == null || localHostName.length() <= 0) {
                                InetAddress localHost = InetAddress.getLocalHost();
                                localHostName = localHost.getHostName();
                                // if we can't get our name, use local address literal
                                if (localHostName == null)
                                        // XXX - not correct for IPv6
                                        localHostName = "[" + localHost.getHostAddress() + "]";
                        }
                } catch (UnknownHostException uhex) {
                }
                return localHostName;
        }

可以看到hostname的獲取可以通過(guò)當(dāng)前連接的session屬性中獲取，也可以從當(dāng)前服務(wù)器的hosts配置中獲取，而我們程序是沒(méi)有在session中設(shè)置hostname的，因此原因肯定在于該臺(tái)Linux服務(wù)器的hosts文件被修改，造成JAVA程序無(wú)法自動(dòng)獲得localhostName。

5. 查看/etc/hosts文件，情況如下：

復(fù)制代碼代碼如下:

127.0.0.1              localhost.localdomain localhost
::1             localhost6.localdomain6 localhost6

簡(jiǎn)單的將hosts文件修改如下：

復(fù)制代碼代碼如下:

127.0.0.1       localhost
::1             localhost6.localdomain6 localhost6

6. 重新測(cè)試，問(wèn)題解決了。
其實(shí)，這種情況也可以通過(guò)程序避免，即在session連接中加入當(dāng)前服務(wù)器的hostname屬性，程序示例：

復(fù)制代碼代碼如下:

        public static void main(String[] args) {
                try {
                        int smtpport = 25;
                        String smtpserver = "219.147.xxx.xxx";
                        Properties prop = System.getProperties();
                        prop.put("mail.smtp.auth", "true");
                        prop.put("mail.smtp.localhost", "myMailServer");
                        Session mailSession = Session.getInstance(prop, null);
                        Transport transport = mailSession.getTransport("smtp");
                        transport.connect(smtpserver,smtpport, "username", "password");
                        System.out.println("connect ok");
                        transport.close();
                } catch (AuthenticationFailedException en) {
                        en.printStackTrace();
                        System.out.println("smtp服務(wù)器連接失敗,請(qǐng)檢查輸入信息是否正確");
                } catch (NoSuchProviderException e) {
                        e.printStackTrace();
                        System.out.println("smtp服務(wù)器連接失敗,請(qǐng)檢查輸入信息是否正確");
                } catch (MessagingException e) {
                        e.printStackTrace();
                        System.out.println("smtp服務(wù)器連接失敗,請(qǐng)檢查輸入信息是否正確");
                }
        }