==== REQUIRED BASIC INFO OF YOUR IREDMAIL SERVER ====
- iRedMail version (check /etc/iredmail-release):  iRedMail-1.6.2
- Deployed with iRedMail Easy or the downloadable installer? downloadable installer
- Linux/BSD distribution name and version: Ubuntu 20.04.3 LTS
- Store mail accounts in which backend (LDAP/MySQL/PGSQL): PGSQL
- Web server (Apache or Nginx): Nginx
- Manage mail accounts with iRedAdmin-Pro? No
- [IMPORTANT] Related original log or error message is required if you're experiencing an issue.
====

在相同的邮件域下，一个账号给另一个账号发送邮件，尝试多次都无法成功收到，但内部的其他人之间是可以正常发送邮件的。
查看了/var/log/iredapd/下的iredapd.log文件，显示的日志如下：

Feb  1 00:57:14 mail iredapd [127.0.0.1] RCPT, 1.jia@*.com => 2.yang@*.com, DUNNO [sasl_username=1.jia@*.com, sender=1.jia@*.com, client_name=mail.*.com, reverse_client_name=mail.*.com, helo=localhost, encryption_protocol=TLSv1.3, encryption_cipher=TLS_AES_256_GCM_SHA384, server_port=587, process_time=0.0202s]
Feb  1 00:57:14 mail iredapd [127.0.0.1] END-OF-MESSAGE, 1.jia@*.com => 2.yang@*.com, DUNNO [recipient_count=1, size=3041606, process_time=0.0149s]

查看了数据库日志，有很多could not receive data from client: Connection reset by peer的日志：

2023-02-01 01:08:30.083 UTC [3960235] vmailadmin@vmail LOG:  could not receive data from client: Connection reset by peer
2023-02-01 01:08:30.083 UTC [3960234] vmailadmin@vmail LOG:  could not receive data from client: Connection reset by peer
2023-02-01 01:08:30.083 UTC [3960233] vmailadmin@vmail LOG:  could not receive data from client: Connection reset by peer
2023-02-01 01:20:24.479 UTC [3963681] vmailadmin@vmail LOG:  could not receive data from client: Connection reset by peer
2023-02-01 01:20:24.479 UTC [3963680] vmailadmin@vmail LOG:  could not receive data from client: Connection reset by peer
2023-02-01 01:20:24.479 UTC [3963059] vmail@vmail LOG:  could not receive data from client: Connection reset by peer
2023-02-01 01:20:24.479 UTC [3963058] vmail@vmail LOG:  could not receive data from client: Connection reset by peer

查看了dovecot的日志，有很多的报错信息：
Feb  1 01:06:52 mail dovecot: auth: Warning: sqlpool(pgsql): Query failed, retrying: FATAL:  terminating connection due to administrator command
Feb  1 01:06:52 mail dovecot: auth: Error: sqlpool(pgsql): Query failed, aborting: SELECT mailbox.password, mailbox.allow_nets FROM mailbox,domain WHERE mailbox.username='2.yang@*.com' AND mailbox."enableimaptls"=1 AND mailbox.active=1 AND mailbox.domain=domain.domain AND domain.backupmx=0 AND domain.active=1
Feb  1 01:06:52 mail dovecot: auth: Error: sql(2.yang@*.com,172.16.2.20,<Wm1LEJnzIXasEAIU>): Password query failed: FATAL:  terminating connection due to administrator command
Feb  1 01:06:59 mail dovecot: auth: Error: pgsql(127.0.0.1): Connect failed to database vmail: could not connect to server: Connection refused
Feb  1 01:06:59 mail dovecot: auth: Error: #011Is the server running on host "127.0.0.1" and accepting
Feb  1 01:06:59 mail dovecot: auth: Error: #011TCP/IP connections on port 5432? (state: connecting)
Feb  1 01:06:59 mail dovecot: auth: Error: pgsql(127.0.0.1): Connect failed to database vmail: could not connect to server: Connection refused
Feb  1 01:06:59 mail dovecot: auth: Error: #011Is the server running on host "127.0.0.1" and accepting
Feb  1 01:06:59 mail dovecot: auth: Error: #011TCP/IP connections on port 5432? (state: connecting)
Feb  1 01:06:59 mail dovecot: auth: Error: pgsql(127.0.0.1): Connect failed to database vmail: could not connect to server: Connection refused

期间我在网上搜索了一些解决方案，做了一次apt-get upgrade，不确定其中的部分数据库报错是否与此有关。