报错如下，翻遍百度居然找不到解决方案
aliasesdb[26660]: /usr/sbin/postconf: error while loading shared libraries: libmysqlclient.so.18: cannot open shared object file: No such file or directory aliasesdb[26660]: /usr/bin/newaliases: error while loading shared libraries: libmysqlclient.so.18: cannot open shared object file: No such file or directory postfix[26668]: /usr/sbin/postfix: error while loading shared libraries: libmysqlclient.so.18: cannot open shared object file: No such file or directory systemd[1]: postfix.service: control process exited, code=exited status=127 systemd[1]: Failed to start Postfix Mail Transport Agent. -- Subject: Unit postfix.service has failed -- Defined-By: systemd
原因就是 libmysqlclient.so.18: cannot open shared object file: No such file or directory
根本原因是没装MySQL，CentOS 7 默认是mariadb
如何不装MySQL解决呢？
yum install -y dovecot mariadb-server dovecot-mysql
至于中间那个 mariadb-server 能不能去掉，就得你试试了，我这是启动了，试不成了
出自：CentOS 7 – Mail Server with Postfix | Devopspoints
