ERROR 1698 (28000): Access denied for user 'root'@'localhost'

I'm setting up a new server and keep running into this problem. When I try to log into the MySQL database with the root user, I get the error: > ERROR 1698 (28000): Access denied for user 'root'@'localhost' It doesn't matter if I connect through the terminal (SSH), through [phpMyAdmin][1] or a MySQL client, e.g., [Navicat][2]. They all fail. I looked in the *mysql.user* table and get the following: ```lang-none +------------------+-------------------+ | user | host | +------------------+-------------------+ | root | % | | root | 127.0.0.1 | | amavisd | localhost | | debian-sys-maint | localhost | | iredadmin | localhost | | iredapd | localhost | | mysql.sys | localhost | | phpmyadmin | localhost | | root | localhost | | roundcube | localhost | | vmail | localhost | | vmailadmin | localhost | | amavisd | test4.folkmann.it | | iredadmin | test4.folkmann.it | | iredapd | test4.folkmann.it | | roundcube | test4.folkmann.it | | vmail | test4.folkmann.it | | vmailadmin | test4.folkmann.it | +------------------+-------------------+ ``` As you can see, user *root* should have access. The Server is quite simple, as I have tried to troubleshoot this for a while now. It's running [Ubuntu 16.04.1][3] LTS (Xenial Xerus) with Apache, MySQL and PHP, so that it can host websites, and iRedMail 0.9.5-1, so that it can host mail. Log into the MySQL database works fine before I installed iRedMail. I also tried just installing iRedMail, but then root also doesn't work. How can I fix my MySQL login problem or how can I install iRedMail over an existing MySQL install? And yes, I tried the [Installation Tips][4] and I can't find those variables in the configuration files. [1]: https://en.wikipedia.org/wiki/PhpMyAdmin [2]: https://en.wikipedia.org/wiki/Navicat [3]: https://en.wikipedia.org/wiki/Ubuntu_version_history#Ubuntu_16.04_LTS_.28Xenial_Xerus.29 [4]: https://code.google.com/archive/p/iredmail/wikis/Installation_Tips.wiki