Postfix与Dovecot配置公共共享邮箱（support/contact）无法接收外部邮件问题求助

大家好，我现在碰到个头疼的问题：想搭建support@domain.extension、contact@domain.extension这类公共共享邮箱，让外部能发邮件进来，同时内部用户可以通过Dovecot的共享文件夹访问这些邮箱内容。目前卡在Postfix和Dovecot的衔接环节，邮件一直退信，想请各位帮忙看看哪里配置出错了。

已完成的Dovecot共享文件夹配置 #

我已经在Dovecot的15-mailboxes.conf里配置了共享命名空间，内部用户能看到Shared目录下的support和contact文件夹，并且用ACL控制访问权限：

namespace {
  type = shared
  separator = /
  prefix = Shared/
  location = mbox:/mail/shared
  subscriptions = no
  list = children

  mailbox support {
    auto = subscribe
  }

  mailbox contact {
    auto = subscribe
  }
}

Postfix的配置尝试与冲突问题 #

为了让support和contact邮箱能接收外部邮件，我创建了/etc/postfix/virtualmaps文件，内容如下：

support@domain.extension support
contact@domain.extension contact

之后执行了postmap /etc/postfix/virtualmaps生成映射库。

接着在main.cf里添加了这些配置：

virtual_mailbox_base = /mail/shared
virtual_mailbox_maps = lmdb:/etc/postfix/virtualmaps

但如果加上virtual_mailbox_domains = $mydomain，Postfix就报错说mydestination和virtual_mailbox_domains不能指向同一个域名，这部分不敢随便修改。另外，所有用户都是LDAP用户，不是系统本地用户。

后续调整及新问题 #

后来根据提示尝试调整local_recipient_maps，还配置了local_delivery把邮件转交给Dovecot，但还是没解决问题：

• 仅启用local_recipient_maps时，Postfix直接返回“unknown user: support”
• 加上local_delivery后，Postfix把邮件转给Dovecot，但Dovecot提示找不到LDAP用户“support@domain.test”

我也参考了Dovecot官方的共享邮箱文档，但还是没找到解决方案。

相关日志信息 #

仅启用local_recipient_maps时的日志：

2023-07-17T14:18:21.117842+02:00 tst postfix/pickup[5200]: 1CA20213BC0: uid=0 from=<testmail@domain.test>
2023-07-17T14:18:21.127591+02:00 tst postfix/cleanup[5212]: 1CA20213BC0: message-id=<64b5318d.5XutEBb44MdWM3yJ%testmail@domain.test>
2023-07-17T14:18:21.167058+02:00 tst postfix/qmgr[5199]: 1CA20213BC0: from=<testmail@domain.test>, size=449, nrcpt=1 (queue active)
2023-07-17T14:18:21.230250+02:00 tst postfix/local[5214]: 1CA20213BC0: to=<support@domain.test>, relay=local, delay=0.13, delays=0.06/0.03/0/0.03, dsn=5.1.1, status=bounced (unknown user: "support")
2023-07-17T14:18:21.231069+02:00 tst postfix/cleanup[5212]: 38487213BC2: message-id=<20230717121821.38487213BC2@tst.nru.test>
2023-07-17T14:18:21.233902+02:00 tst postfix/bounce[5215]: 1CA20213BC0: sender non-delivery notification: 38487213BC2
2023-07-17T14:18:21.233966+02:00 tst postfix/qmgr[5199]: 38487213BC2: from=<>, size=2226, nrcpt=1 (queue active)
2023-07-17T14:18:21.234323+02:00 tst postfix/qmgr[5199]: 1CA20213BC0: removed
2023-07-17T14:18:21.235893+02:00 tst postfix/local[5214]: 38487213BC2: to=<testmail@domain.test>, relay=local, delay=0.01, delays=0/0/0/0, dsn=2.0.0, status=sent (delivered to mailbox)

启用local_recipient_maps和local_delivery时的日志：

2023-07-20T13:09:48.958737+02:00 tst postfix/qmgr[31655]: 274CA215D35: from=<testmail@domain.test>, size=449, nrcpt=1 (queue active)
2023-07-20T13:09:48.993036+02:00 tst dovecot: lda(support@domain.test)<31682><>: Debug: Loading modules from directory: /usr/lib64/dovecot/modules
2023-07-20T13:09:48.993428+02:00 tst dovecot: lda(support@domain.test)<31682><>: Debug: Module loaded: /usr/lib64/dovecot/modules/lib01_acl_plugin.so
2023-07-20T13:09:48.993549+02:00 tst dovecot: lda(support@domain.test)<31682><>: Debug: auth-master: userdb lookup(support@domain.test): Started userdb lookup
2023-07-20T13:09:48.993643+02:00 tst dovecot: lda(support@domain.test)<31682><>: Debug: auth-master: conn unix:/var/run/dovecot//auth-userdb: Connecting
2023-07-20T13:09:48.993756+02:00 tst dovecot: lda(support@domain.test)<31682><>: Debug: auth-master: conn unix:/var/run/dovecot//auth-userdb (pid=26599,uid=0): Client connected (fd=8)
2023-07-20T13:09:48.996561+02:00 tst dovecot: lda(support@domain.test)<31682><>: Debug: auth-master: userdb lookup(support@domain.test): auth USER input:
2023-07-20T13:09:48.996672+02:00 tst dovecot: lda(support@domain.test)<31682><>: Debug: auth-master: userdb lookup(support@domain.test): Userdb lookup failed
2023-07-20T13:09:48.996765+02:00 tst dovecot: lda(31682): Debug: auth-master: conn unix:/var/run/dovecot//auth-userdb (pid=26599,uid=0): Disconnected: Connection closed (fd=8)
2023-07-20T13:09:49.003457+02:00 tst postfix/pipe[31681]: 274CA215D35: to=<support@domain.test>, relay=dovecot, delay=903, delays=903/0.01/0/0.03, dsn=5.1.1, status=bounced (user unknown. Command output: lda(support@domain.test): Error: net_connect_unix(/var/run/dovecot//stats-writer) failed: Permission denied )
2023-07-20T13:09:49.009715+02:00 tst postfix/cleanup[31684]: 0233E215EBD: message-id=<20230720110949.0233E215EBD@tst.nru.test>
2023-07-20T13:09:49.012518+02:00 tst postfix/bounce[31683]: 274CA215D35: sender non-delivery notification: 0233E215EBD
2023-07-20T13:09:49.012577+02:00 tst postfix/qmgr[31655]: 0233E215EBD: from=<>, size=2430, nrcpt=1 (queue active)
2023-07-20T13:09:49.012611+02:00 tst postfix/qmgr[31655]: 274CA215D35: removed
2023-07-20T13:09:49.022166+02:00 tst dovecot: lda(testmail@domain.test)<31685><>: Debug: Loading modules from directory: /usr/lib64/dovecot/modules
2023-07-20T13:09:49.022500+02:00 tst dovecot: lda(testmail@domain.test)<31685><>: Debug: Module loaded: /usr/lib64/dovecot/modules/lib01_acl_plugin.so
2023-07-20T13:09:49.022610+02:00 tst dovecot: lda(testmail@domain.test)<31685><>: Debug: auth-master: userdb lookup(testmail@domain.test): Started userdb lookup
2023-07-20T13:09:49.022700+02:00 tst dovecot: lda(testmail@domain.test)<31685><>: Debug: auth-master: conn unix:/var/run/dovecot//auth-userdb: Connecting
2023-07-20T13:09:49.022821+02:00 tst dovecot: lda(testmail@domain.test)<31685><>: Debug: auth-master: conn unix:/var/run/dovecot//auth-userdb (pid=26599,uid=0): Client connected (fd=8)
2023-07-20T13:09:49.025074+02:00 tst dovecot: lda(testmail@domain.test)<31685><>: Debug: auth-master: userdb lookup(testmail@domain.test): auth USER input:
2023-07-20T13:09:49.025181+02:00 tst dovecot: lda(testmail@domain.test)<31685><>: Debug: auth-master: userdb lookup(testmail@domain.test): Userdb lookup failed
2023-07-20T13:09:49.025271+02:00 tst dovecot: lda(31685): Debug: auth-master: conn unix:/var/run/dovecot//auth-userdb (pid=26599,uid=0): Disconnected: Connection closed (fd=8)
2023-07-20T13:09:49.027037+02:00 tst postfix/pipe[31681]: 0233E215EBD: to=<testmail@domain.test>, relay=dovecot, delay=0.02, delays=0.01/0/0/0.01, dsn=5.1.1, status=bounced (user unknown. Command output: lda(testmail@domain.test): Error: net_connect_unix(/var/run/dovecot//stats-writer) failed: Permission denied )
2023-07-20T13:09:49.027394+02:00 tst postfix/qmgr[31655]: 0233E215EBD: removed

现在实在找不到问题根源了，有没有大佬能指点一下，怎么让Postfix把邮件正确投递到Dovecot的共享邮箱里，同时不影响现有LDAP用户的邮件接收？

备注：内容来源于stack exchange，提问作者Kiwimarc