用PYTHON实现一个邮件客户端类，可以接收邮件，可以发送邮件，可以删除邮件，可以获取未阅读邮件，可以给邮件做标记

好的，这是一个简单的邮件客户端类的实现：

import imaplib
import email

class MailClient:
    def __init__(self, host, username, password):
        self.host = host
        self.username = username
        self.password = password
        self.mailbox = imaplib.IMAP4_SSL(self.host)
        self.mailbox.login(self.username, self.password)

    def send_mail(self, to, subject, body):
        # 使用smtplib模块发送邮件
        import smtplib
        from email.mime.text import MIMEText

        msg = MIMEText(body)
        msg['Subject'] = subject
        msg['From'] = self.username
        msg['To'] = to

        server = smtplib.SMTP_SSL(self.host)
        server.login(self.username, self.password)
        server.send_message(msg)
        server.quit()

    def list_mailboxes(self):
        # 列出所有邮箱
        status, mailbox_list = self.mailbox.list()
        return mailbox_list

    def select_mailbox(self, mailbox):
        # 选择要操作的邮箱
        self.mailbox.select(mailbox)

    def search_mail(self, criteria):
        # 根据条件搜索邮件
        status, msg_ids = self.mailbox.search(None, criteria)
        return msg_ids[0].split()

    def fetch_mail(self, msg_id):
        # 获取邮件内容
        status, msg_data = self.mailbox.fetch(msg_id, "(RFC822)")
        msg = email.message_from_bytes(msg_data[0][1])
        return msg

    def delete_mail(self, msg_id):
        # 删除邮件
        self.mailbox.store(msg_id, "+FLAGS", "\\Deleted")
        self.mailbox.expunge()

    def mark_mail(self, msg_id, flag):
        # 给邮件添加标记
        self.mailbox.store(msg_id, "+FLAGS", flag)

    def close_mailbox(self):
        # 关闭邮箱
        self.mailbox.close()
        self.mailbox.logout()

使用方法如下：

# 创建邮件客户端对象
client = MailClient("imap.example.com", "username", "password")

# 发送邮件
client.send_mail("to@example.