现在测试的情况比较明确了，是我在分离数据库的时候有东西没修改完全导致认证时候连接数据库失败造成。

测试反馈后还是不行
或者干脆这样子可行否
数据库先安装好并配置好root的远程密码及访问权限，然后参照远程mysql存在的情况下重新安装iredmail。。。

在/etc/dovecot/dovecot.conf下找到：
=====================================
# Virtual mail accounts.
userdb {
    args = /etc/dovecot/dovecot-mysql.conf
    driver = sql
}
passdb {
    args = /etc/dovecot/dovecot-mysql.conf
    driver = sql
}
====================================
这个文件应该是负责虚拟账户密码的认证？
于是打开：/etc/dovecot/dovecot-mysql.conf
里面已修改为远程mysql的账户：
====================================
driver = mysql
default_pass_scheme = CRYPT
connect = host=192.168.0.55 dbname=vmail user=vmail password=38ffGTLRuN30SHkbRqqeBOQW2dp9KO
# Required by 'doveadm mailbox ...'.
iterate_query = SELECT username AS user FROM mailbox
password_query = SELECT password, allow_nets FROM mailbox WHERE username='%u' AND enable%Ls%Lc=1 AND active=1
user_query = SELECT
..........
====================================
密码没修改，数据库是从未分离之前全备过去的，同时给每个账户开启了远程访问权限。会是不是密码的问题？【这个密码和下面查出来的mysql.user表里的长度都不一样】
原始机器上的mysql数据库账户信息：
====================================
mysql> select user,host,password from mysql.user;
+-------------+-----------+-------------------------------------------+
| user        | host      | password                                  |
+-------------+-----------+-------------------------------------------+
| root        | localhost | *C5273F332068F030D6E6A584584C5A5217471879 |
| vmail       | localhost | *434A32827A46D81E51B564F5DA5103408F52D26C |
| vmailadmin  | localhost | *421CFB94E48FFB20BC2C054983DE501B4717D364 |
| cluebringer | localhost | *6E5DFF5B05EB44F4C6C3D3813800B9DE607260C7 |
| amavisd     | localhost | *5400FCD9F745AE7776ACC2298C22C1FD6D29675E |
| iredadmin   | localhost | *DB076D83C9301B2A027CAD2D08EADA66E56E25CD |
| roundcube   | localhost | *E345D25AD8A912B45A5EC4D4181EEBD3F47AD942 |
+-------------+-----------+-------------------------------------------+
7 rows in set (0.00 sec)
====================================
远程mysql服务器的账户信息：
====================================
mysql> select user,host,password from mysql.user;
+-------------+-----------+-------------------------------------------+
| user        | host      | password                                  |
+-------------+-----------+-------------------------------------------+
| root        | localhost | *C5273F332068F030D6E6A584584C5A5217471879 |
| vmail       | %         | *434A32827A46D81E51B564F5DA5103408F52D26C |
| amavisd     | %         | *5400FCD9F745AE7776ACC2298C22C1FD6D29675E |
| vmailadmin  | %         | *421CFB94E48FFB20BC2C054983DE501B4717D364 |
| cluebringer | %         | *6E5DFF5B05EB44F4C6C3D3813800B9DE607260C7 |
| roundcube   | %         | *E345D25AD8A912B45A5EC4D4181EEBD3F47AD942 |
| iredadmin   | %         | *DB076D83C9301B2A027CAD2D08EADA66E56E25CD |
+-------------+-----------+-------------------------------------------+
====================================

如果还需要什么信息，我再补全。