Gmail API无法读取SMTP协议发送的邮件问题咨询

通过Python脚本使用SMTP协议发送内容为This is an email test的邮件，在Gmail网页端收件箱中可见，但使用Gmail API读取时无法获取到该邮件；而通过Gmail网页发送相同内容的邮件，API可以正常读取并输出正文。

发送邮件的Python代码 #

def send_email(subject, body):
            global host, app_password
            msg = MIMEText(body)
            msg['Subject'] = subject
            msg['From'] = host
            msg['To'] = host
            with smtplib.SMTP_SSL('smtp.gmail.com', 465) as smtp_server:
                smtp_server.login(host, app_password)
                smtp_server.sendmail(host, host, msg.as_string())

读取邮件的Python代码 #

def get_messages():

    # Verify Credentials and Token 
    creds = None
    if os.path.exists('token.pickle'): 
        with open('token.pickle', 'rb') as token:
            creds = pickle.load(token)  
    if not creds or not creds.valid: 
        if creds and creds.expired and creds.refresh_token: 
            creds.refresh(Request()) 
        else: 
            flow = InstalledAppFlow.from_client_secrets_file('C:\\my\\path\\to\\credentials\\credentials.json', SCOPES) 
            creds = flow.run_local_server(port=0) 
        with open('token.pickle', 'wb') as token: 
            pickle.dump(creds, token) 
  
    # Connect to the Gmail API 
    service = build('gmail', 'v1', credentials=creds) 
    result = service.users().messages().list(userId='me').execute() 
    messages = result.get('messages') 
  
    # Loop through emails
    try:
        for msg in messages: 
            txt = service.users().messages().get(userId='me', id=msg['id']).execute()  
            payload = txt['payload'] 
            headers = payload['headers']

            # Extract values from data
            for d in headers: 
                if d['name'] == 'Subject': 
                    subject = d['value'] 
                if d['name'] == 'From': 
                    sender = d['value'] 
            parts = payload.get('parts')[0] 
            data = parts['body']['data'] 
            data = data.replace("-","+").replace("_","/") 
            decoded_data = base64.b64decode(data) 
            soup = BeautifulSoup(decoded_data, "lxml") 
            body = soup.body() 

            # Output
            if sender=='Bote <'+host+'>':
                print(subject)
                if subject==code:
                    print(body[4:-5])
        if back==True:
            return
    except:
        pass

• 发送者头匹配不匹配：SMTP发送的邮件From头仅为纯邮箱地址（即host变量的值），但读取代码中硬编码判断sender=='Bote <'+host+'>'——只有网页发送的邮件才会附带Bote这个昵称，因此SMTP发送的邮件直接被过滤，无法进入输出逻辑。
• 邮件结构处理逻辑缺陷：SMTP发送的纯文本邮件（MIMEText构造），Gmail API返回的payload结构中没有parts字段，正文数据直接存储在payload['body']中。但读取代码强行调用payload.get('parts')[0]，会触发索引错误，而宽泛的try-except直接跳过了该邮件的处理，没有任何提示。
• 异常捕获过于宽泛：代码使用try:... except: pass捕获所有异常，导致结构不匹配、变量未定义等错误都被隐藏，无法定位具体问题。

1. 修正发送者判断逻辑
   放弃硬编码昵称，改为匹配邮箱地址本身，示例：

   # 提取sender中的邮箱地址，兼容带昵称和纯邮箱的格式
   import re
   sender_email = re.search(r'<(.+?)>', sender).group(1) if '<' in sender else sender
   if sender_email == host:
       print(subject)
       if subject == code:
           print(body.get_text())  # 改用get_text()获取正文
   

   或者简化判断：

   if host in sender:
       # 后续输出逻辑
   

2. 兼容不同邮件结构
   处理正文时先判断是否存在parts字段，兼容纯文本和多部件邮件：

   # 读取邮件正文数据
   if 'parts' in payload:
       data = payload['parts'][0]['body']['data']
   else:
       data = payload['body']['data']
   data = data.replace("-","+").replace("_","/")
   decoded_data = base64.b64decode(data)
   soup = BeautifulSoup(decoded_data, "lxml")
   body = soup.get_text()  # 用get_text()替代body()，更稳定获取纯文本内容
   

3. 优化异常处理
   仅捕获特定异常或打印错误信息，方便调试：

   try:
       # 原有邮件处理逻辑
   except Exception as e:
       print(f"处理邮件ID {msg['id']} 时出错: {str(e)}")
   

4. 可选：指定收件箱标签
   调用messages().list()时明确指定读取收件箱邮件，避免遗漏：

   result = service.users().messages().list(userId='me', labelIds=['INBOX']).execute()
   

内容的提问来源于stack exchange，提问作者Markas M