使用Python调用Gmail API发送邮件被标记为垃圾/钓鱼邮件且缺少签名的问题求助

我刚学会用Python脚本调用Gmail API自动发送邮件，目前功能正常，但遇到两个棘手的问题：

• 用这种方式发送的邮件都会被标记为「可能是垃圾邮件或钓鱼邮件」，导致部分服务器可能直接拦截它们
• 发送的邮件里没有显示我的邮箱签名

我猜测这两个问题应该是相关的，可能是因为API调用没有走完整的账号身份验证流程，没能正确关联到我的主邮箱，但我试了好几种方法都没能解决。

下面是我实际使用的代码：

import os
import pickle

#Gmail API utils
from googleapiclient.discovery import build
from google_auth_oauthlib.flow import InstalledAppFlow
from google.auth.transport.requests import Request

# for encoding/decoding messages in base64
from base64 import urlsafe_b64decode, urlsafe_b64encode

# for dealing with attachment MIME types
from email.mime.text import MIMEText
from email.mime.multipart import MIMEMultipart
from email.mime.image import MIMEImage
from email.mime.audio import MIMEAudio
from email.mime.base import MIMEBase
from mimetypes import guess_type as guess_mime_type

# Request all access (permission to read/send/receive emails, manage the inbox, and more)
SCOPES = ['https://mail.google.com/']
my_email = 'sample@gmail.com'

def gmail_authenticate():

    creds = None

    # the file token.pickle stores the user's access and refresh tokens, and is
    # created automatically when the authorization flow completes for the first time

    if os.path.exists("token.pickle"):
        with open("token.pickle", "rb") as token:
            creds = pickle.load(token)

        # if there are no (valid) credentials available, let the user log in.
        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('credentials.json', SCOPES)
                creds = flow.run_local_server(port=0)
            # save the credentials for the next run
            with open("token.pickle", "wb") as token:
                pickle.dump(creds, token)
        return build('gmail', 'v1', credentials=creds)

# get the Gmail API service
service = gmail_authenticate()

# Adds the attachment with the given filename to the given message
def add_attachment(message, filename):
    content_type, encoding = guess_mime_type(filename)
    if content_type is None or encoding is not None:
        content_type = 'application/octet-stream'
    main_type, sub_type = content_type.split('/', 1)
    if main_type == 'text':
        fp = open(filename, 'rb')
        msg = MIMEText(fp.read().decode(), _subtype=sub_type)
        fp.close()
    elif main_type == 'image':
        fp = open(filename, 'rb')
        msg = MIMEImage(fp.read(), _subtype=sub_type)
        fp.close()
    elif main_type == 'audio':
        fp = open(filename, 'rb')
        msg = MIMEAudio(fp.read(), _subtype=sub_type)
        fp.close()
    else:
        fp = open(filename, 'rb')
        msg = MIMEBase(main_type, sub_type)
        msg.set_payload(fp.read())
        fp.close()
    filename = os.path.basename(filename)
    msg.add_header('Content-Disposition', 'attachment', filename=filename)
    message.attach(msg)

def build_message(destination, obj, body, attachments=[]):
    if not attachments:  # no attachments given
        message = MIMEText(body)
        message['to'] = destination
        message['from'] = my_email
        message['subject'] = obj
    else:
        message = MIMEMultipart()
        message['to'] = destination
        message['from'] = my_email
        message['subject'] = obj
        message.attach(MIMEText(body))
        for filename in attachments:
            add_attachment(message, filename)
    return {'raw': urlsafe_b64encode(message.as_bytes()).decode()}

def send_message(serv, destination, obj, body, attachments=[]):
    return serv.users().messages().send(
        userId="me",
        body=build_message(destination, obj, body, attachments)
    ).execute()

send_message(service, my_email, "Test subject", "This is the body of the e-mail")

有没有大佬能帮忙看看怎么解决这两个问题？非常感谢！

备注：内容来源于stack exchange，提问作者Flavio Fernandes