帮我写一个处理已的解析复杂的下载好的邮件系统，Python语言

在Python中，设计一个复杂的邮件下载和管理系统通常会涉及IMAP（Internet Message Access Protocol）库，例如`imaplib`，以及SMTP（Simple Mail Transfer Protocol）库，如`smtplib`。这里是一个简化的示例，展示如何使用这两个库读取和管理邮件：

import imaplib
import email
from email.header import decode_header

# 连接到IMAP服务器
def login_imap(user, password, host='imap.example.com', port=993):
    imap = imaplib.IMAP4_SSL(host, port)
    imap.login(user, password)
    return imap

def fetch_emails(imap, mailbox='INBOX'):
    # SELECT指定邮箱
    imap.select(mailbox)

    # 获取邮件列表
    typ, data = imap.search(None, 'ALL')
    mail_ids = data[0].split(b'\n')

    emails = []
    for id in mail_ids:
        _, msg_data = imap.fetch(id, '(RFC822)')
        raw_email = msg_data[0][1]
        email_message = email.message_from_bytes(raw_email)
        emails.append(process_email(email_message))

    return emails

def process_email(email_msg):
    # 解析邮件头信息
    subject, encoding = decode_header(email_msg['Subject'])[0]
    if isinstance(subject, bytes):
        subject = subject.decode(encoding)

    sender = email.utils.parseaddr(email_msg['From'])[1]
    body = ''
    if email_msg.is_multipart():
        for part in email_msg.walk():
            content_type = part.get_content_type()
            if content_type == 'text/plain':
                body += part.get_payload(decode=True).decode('utf-8')
    else:
        body = email_msg.get_payload(decode=True).decode('utf-8')

    return {
        'subject': subject,
        'sender': sender,
        'body': body
    }

def main():
    user = 'your_username'
    password = 'your_password'

    imap = login_imap(user, password)
    fetched_emails = fetch_emails(imap)
    for email in fetched_emails:
        print(f"Subject: {email['subject']}, Sender: {email['sender']} - Body: {email['body']}")

    imap.close()
    imap.logout()

if __name__ == "__main__":
    main()

这个脚本首先连接到IMAP服务器并登录用户，然后从指定的邮箱（通常是`INBOX`）获取所有邮件，并对每个邮件进行解析，提取主题、发件人和正文内容。请注意，实际应用可能需要处理更复杂的情况，比如错误处理、分页查询等。