Fuglu插件中如何向发件人发送自定义退信消息？

问题1：Fuglu 0.10版本中同时处理允许/拒绝收件人列表的逻辑问题 #

问题描述 #

维护允许/拒绝收件人列表时，尝试向拒绝列表收件人发送退信，同时向允许列表收件人投递邮件，但因邮件处理流程只能返回一个状态值，当前代码逻辑存在冲突，导致允许列表的邮件无法正常投递。

现有代码 #

if allow_group_list:
    suspect.recipients = allow_group_list
    self._logger().info(
        '888 ==== allowed suspect.recipients: %s' %(suspect.recipients))

if deny_group_list:
    suspect.recipients = deny_group_list
    self._logger().info(
        '9999 ====== denied suspect.recipients: %s' %(suspect.recipients))
    self.send_bounce_message(suspect,deny_group_list,msubject)
    self._mark_bounce_sent(message_id, deny_group_list,msubject)
    return REJECT

return DUNNO

def send_bounce_message(self, suspect,mto,msubject):
    blockinfo = 'Please add the specific user and resend'
    queueid = suspect.get_tag('specificuser.bounce.queueid')
    #suspect.set_tag(mto_address,suspect.recipient)
    if queueid:
        self._logger().info(
            f'{suspect.id} already sent specific user block bounce '
            f'to {suspect.from_address} with queueid {queueid}')
    else: #tmm
        self._logger().info(f"{suspect.id} sending specific user block "
                            f"bounce to {suspect.from_address}")
        bounce = Bounce(self.config)
        queueid = bounce.send_template_file(suspect.from_address,
                                            self.template_bounce,
                                            suspect,
                                            {'blockinfo':blockinfo,
                                             'mto':mto,
                                             'msubject':msubject
                                            })
        suspect.set_tag('specificuser.bounce.queueid', queueid)

问题分析 #

1. 若同时存在允许和拒绝列表，代码会先将suspect.recipients设为允许列表，随后又覆盖为拒绝列表，最终返回REJECT，导致允许列表的邮件也被拒绝。
2. 手动调用退信方法后直接返回REJECT，终止了后续流程，允许列表的邮件无法进入投递环节。

解决方案 #

拆分收件人处理逻辑，分离允许列表的投递和拒绝列表的退信操作：

# 从原始收件人中拆分允许/拒绝列表
original_recipients = suspect.recipients.copy()
# 替换为你的实际允许/拒绝数据源
allow_group_list = [rcpt for rcpt in original_recipients if rcpt in self.allowed_list]
deny_group_list = [rcpt for rcpt in original_recipients if rcpt in self.denied_list]

if allow_group_list:
    suspect.recipients = allow_group_list
    self._logger().info('888 ==== allowed suspect.recipients: %s' % suspect.recipients)

if deny_group_list:
    self._logger().info('9999 ====== denied recipients to bounce: %s' % deny_group_list)
    # 逐个处理拒绝收件人，避免重复退信
    for rcpt in deny_group_list:
        bounce_tag = f'specificuser.bounce.{rcpt}'
        queueid = suspect.get_tag(bounce_tag)
        if not queueid:
            self._logger().info(f"{suspect.id} sending bounce to {suspect.from_address} for {rcpt}")
            bounce = Bounce(self.config)
            queueid = bounce.send_template_file(
                suspect.from_address,
                self.template_bounce,
                suspect,
                {'blockinfo': 'Please add the specific user and resend',
                 'mto': rcpt,
                 'msubject': msubject
                })
            suspect.set_tag(bounce_tag, queueid)
        self._mark_bounce_sent(message_id, [rcpt], msubject)

# 返回DUNNO让Fuglu继续处理允许列表的邮件投递
return DUNNO

问题2：Fuglu 1.2版本中发件人给自己发邮件时未收到退信 #

问题描述 #

编写插件维护允许/拒绝列表，当收件人在拒绝列表时返回REJECT和自定义消息，但发件人another@y.com给自己发送邮件时，未收到预期的退信。

现有配置及代码 #

fuglu.conf配置

plugins=custom_msg
disablebounces=0
[PluginAlias]
custom_msg=custom_msg.CustomMessagePlugin

custom_msg.py代码

from fuglu.shared import ScannerPlugin, DUNNO, DELETE, Suspect, REJECT

class CustomMessagePlugin(ScannerPlugin):
    def __init__(self, *args, **kwargs):
        ScannerPlugin.__init__(self, *args, **kwargs)
        self.allowed_recipients = ['test9@y.com']
        self.denied_recipients = ['test8@y.com','another@y.com']

    def examine(self, suspect):
        sender = suspect.from_address.lower()
        recipient = suspect.recipients[0].lower()

        if recipient in self.denied_recipients:
            # Send bounce message to the sender
            bounce_message = "Your email to {} has been rejected.".format(recipient)
            return REJECT, bounce_message
        else:
            return DUNNO

    def lint(self):
        return
    
    def __str__(self):
        return "Custom Plugin"

问题分析 #

1. Fuglu默认可能会跳过发件人与收件人相同的退信，避免循环退信。
2. 仅处理第一个收件人，若存在多收件人场景会遗漏；同时返回REJECT的自定义消息是否触发内置退信，需确认版本行为。

解决方案 #

修改插件逻辑，手动发送退信并处理所有收件人：

from fuglu.shared import ScannerPlugin, DUNNO, REJECT, Bounce

class CustomMessagePlugin(ScannerPlugin):
    def __init__(self, *args, **kwargs):
        ScannerPlugin.__init__(self, *args, **kwargs)
        self.allowed_recipients = ['test9@y.com']
        self.denied_recipients = ['test8@y.com','another@y.com']

    def examine(self, suspect):
        sender = suspect.from_address.lower()
        denied_recipients = []
        # 遍历所有收件人，筛选拒绝列表项
        for rcpt in suspect.recipients:
            rcpt_lower = rcpt.lower()
            if rcpt_lower in self.denied_recipients:
                denied_recipients.append(rcpt)
        
        if denied_recipients:
            bounce_msg = "Your email to the following recipients has been rejected: {}".format(', '.join(denied_recipients))
            # 手动发送退信，强制处理发件人等于收件人的场景
            bounce = Bounce(self.config)
            bounce.send(sender, bounce_msg, suspect)
            # 保留未被拒绝的收件人继续投递
            suspect.recipients = [rcpt for rcpt in suspect.recipients if rcpt not in denied_recipients]
            # 无有效收件人则返回REJECT，否则返回DUNNO继续处理
            return REJECT, bounce_msg if not suspect.recipients else DUNNO
        else:
            return DUNNO

    def lint(self):
        return
    
    def __str__(self):
        return "Custom Plugin"

Fuglu退信自定义的技术支持获取途径 #

• 查看Fuglu本地部署的内置文档或源码中的docs、README目录；
• 参考Fuglu源码中的内置插件实现，学习官方的退信处理逻辑；
• 查阅fuglu.conf配置文件的注释，了解退信相关配置项的作用；
• 参与项目代码托管平台的社区讨论，获取其他开发者的经验分享。

内容的提问来源于stack exchange，提问作者user956424