用JavaMail通过IMAP协议接收qq邮箱时出现“A0 BAD 命令无效或者不支持”的解决方法

使用JavaMail通过IMAP协议接收qq邮箱时出现'A0 BAD 命令无效或者不支持'的错误。通过设置mail.imap.auth.login.disable为true，解决了QQ邮箱连接问题。详细步骤包括分析错误信息、尝试不同解决方案，并最终成功连接并获取邮箱消息。

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最开始的java代码如下

import java.io.UnsupportedEncodingException; import java.util.Properties; import javax.mail.Authenticator; import javax.mail.Folder; import javax.mail.MessagingException; import javax.mail.PasswordAuthentication; import javax.mail.Session; import javax.mail.Store; import ce.mail.models.ConnectionProfile; public class ImapProtocolImpl extends Authenticator implements Protocol { private Session session; private PasswordAuthentication authentication; public ImapProtocolImpl(ConnectionProfile profile, String username, String password) { Properties props = new Properties(); props.setProperty("mail.store.protocol", profile.getProtocol()); props.setProperty("mail.imap.host", profile.getFetchServer()); props.setProperty("mail.imap.port", profile.getFetchPort()); authentication = new PasswordAuthentication(username, password); session = Session.getInstance(props, this); } @Override public PasswordAuthentication getPasswordAuthentication() { return this.authentication; } public void connect() { try { Store store = session.getStore(); store.connect(); Folder root = store.getDefaultFolder(); Folder inbox = root.getFolder("inbox"); inbox.open(Folder.READ_WRITE); System.out.println(inbox.getMessageCount()); } catch (MessagingException e) { try { byte[] buf = e.getMessage().getBytes("ISO-8859-1"); System.out.println(new String(buf, "GBK")); } catch (UnsupportedEncodingException e1) { e1.printStackTrace(); } throw new RuntimeException("登录失败", e); } } }

该程序连接163邮箱时是正常的，但连接qq邮箱时会出错。

调用session.setDebug(true);后发现连qq邮箱的debug信息如下

上Google搜“java mail imap qq 邮箱”，发现《JavaMail中接收邮件的问题》里提到，需要设置mail.imap.auth.plain.disable为true，但设置完后仍会出错。

继续搜mail.imap.auth.plain.disable，在api文档中发现另外一个属性mail.imap.auth.login.disable，文档中提到“If true, prevents use of the non-standard AUTHENTICATE LOGIN command, instead using the plain LOGIN command. Default is false.”，而根据debug信息，连接qq邮箱也是在A0 AUTHENTICATE LOGIN之后提示错误，所以明显是这个参数的问题。

设置参数mail.imap.auth.login.disable为true后连接qq邮箱正常，最终程序如下

import java.io.UnsupportedEncodingException; import java.util.Properties; import javax.mail.Authenticator; import javax.mail.Folder; import javax.mail.MessagingException; import javax.mail.PasswordAuthentication; import javax.mail.Session; import javax.mail.Store; import ce.mail.models.ConnectionProfile; public class ImapProtocolImpl extends Authenticator implements Protocol { private Session session; private PasswordAuthentication authentication; public ImapProtocolImpl(ConnectionProfile profile, String username, String password) { Properties props = new Properties(); props.setProperty("mail.store.protocol", profile.getProtocol()); props.setProperty("mail.imap.host", profile.getFetchServer()); props.setProperty("mail.imap.port", profile.getFetchPort()); props.setProperty("mail.imap.auth.login.disable", "true"); authentication = new PasswordAuthentication(username, password); session = Session.getInstance(props, this); session.setDebug(true); } @Override public PasswordAuthentication getPasswordAuthentication() { return this.authentication; } public void connect() { try { Store store = session.getStore(); store.connect(); Folder root = store.getDefaultFolder(); Folder inbox = root.getFolder("inbox"); inbox.open(Folder.READ_WRITE); System.out.println(inbox.getMessageCount()); } catch (MessagingException e) { try { byte[] buf = e.getMessage().getBytes("ISO-8859-1"); System.out.println(new String(buf, "GBK")); } catch (UnsupportedEncodingException e1) { e1.printStackTrace(); } throw new RuntimeException("登录失败", e); } } }

正确的debug信息如下

DEBUG: setDebug: JavaMail version 1.4.3 DEBUG: getProvider() returning javax.mail.Provider[STORE,imap,com.sun.mail.imap.IMAPStore,Sun Microsystems, Inc] DEBUG: mail.imap.fetchsize: 16384 DEBUG: mail.imap.statuscachetimeout: 1000 DEBUG: mail.imap.appendbuffersize: -1 DEBUG: mail.imap.minidletime: 10 DEBUG: disable AUTH=LOGIN DEBUG: trying to connect to host "imap.qq.com", port 143, isSSL false * OK [CAPABILITY IMAP4 IMAP4rev1 AUTH=LOGIN NAMESPACE] QQMail IMAP4Server ready IMAP DEBUG: AUTH: LOGIN DEBUG: protocolConnect login, host=imap.qq.com, user=<qq号码>, password=<non-null> A0 LOGIN <qq号码> <未加密的密码> A0 OK Success login ok A1 CAPABILITY * CAPABILITY IMAP4 IMAP4rev1 NAMESPACE CHILDREN A1 OK CAPABILITY Completed DEBUG: connection available -- size: 1 A2 SELECT inbox * 26 EXISTS * 0 RECENT * OK [UNSEEN 1] * OK [UIDVALIDITY 1295833210] UID validity status * OK [UIDNEXT 29] Predicted next UID * FLAGS (/Answered /Flagged /Deleted /Draft /Seen) * OK [PERMANENTFLAGS (/* /Answered /Flagged /Deleted /Draft /Seen)] Permanent flags A2 OK [READ-WRITE] SELECT complete 26