Gmail（API） - 从1970年开始出现奇怪的空消息

Question

我正在使用Gmail API，而且我正在抓取电子邮件。我的第一步是列出所有线程，然后为每个线程调用get方法。但是，无法通过get方法访问某些列出的线程。

示例错误＃1：

{ Error: Not Found
    at Request._callback (/home/kuno/code/an_api/node_modules/google-auth-library/lib/transporters.js:85:15)
    at Request.self.callback (/home/kuno/code/an_api/node_modules/google-auth-library/node_modules/request/request.js:198:22)
    at emitTwo (events.js:106:13)
    at Request.emit (events.js:191:7)
    at Request.<anonymous> (/home/kuno/code/an_api/node_modules/google-auth-library/node_modules/request/request.js:1057:14)
    at emitOne (events.js:101:20)
    at Request.emit (events.js:188:7)
    at IncomingMessage.<anonymous> (/home/kuno/code/an_api/node_modules/google-auth-library/node_modules/request/request.js:1003:12)
    at emitNone (events.js:91:20)
    at IncomingMessage.emit (events.js:185:7)
  code: 404,
  errors: [ { domain: 'global', reason: 'notFound', message: 'Not Found' } ] }

示例错误＃2：

{ Error: Requested entity was not found.
    at Request._callback (/home/kuno/code/an_api/node_modules/google-auth-library/lib/transporters.js:85:15)
    at Request.self.callback (/home/kuno/code/an_api/node_modules/google-auth-library/node_modules/request/request.js:198:22)
    at emitTwo (events.js:106:13)
    at Request.emit (events.js:191:7)
    at Request.<anonymous> (/home/kuno/code/an_api/node_modules/google-auth-library/node_modules/request/request.js:1057:14)
    at emitOne (events.js:101:20)
    at Request.emit (events.js:188:7)
    at IncomingMessage.<anonymous> (/home/kuno/code/an_api/node_modules/google-auth-library/node_modules/request/request.js:1003:12)
    at emitNone (events.js:91:20)
    at IncomingMessage.emit (events.js:185:7)
  code: 404,
  errors: 
   [ { message: 'Requested entity was not found.',
       domain: 'global',
       reason: 'notFound' } ] }

当我尝试直接从Gmail（浏览器应用）访问这些消息时，它们的外观如下：

附件是一个空的.txt文件。请注意，它是从（void）发送并在1970年发送到（void）。

那些消息是什么？它们为什么会出现？如何过滤/忽略/删除它们？