Connect to a Plesk server via SSH.

Create a copy “postfix” configuration file:

# cp -a /etc/postfix/main.cf /root/backup_main.cf

Open “postfix” configuration file in a text editor, for example, “vi” editor:

# vi /etc/postfix/main.cf

Add the lines specified below to the configuration file main.cf and make sure that these lines are present only once in the file:

Note: replace example.com with required mail server name.

myhostname = example.com
smtpd_banner = $myhostname ESMTP $mail_name

Using command line tool. check “postfix” configuration syntax and restart postfix:

postfix check
(empty output - means syntax is OK)
# service postfix restart

FTP is not working and has the following error:
421 Service not available, remote server has closed connection

Also, in the message logs:
Plesk Unable to FTP – missing scoreboard file (Linux)

On CentOS 6 and 7 if you experience issues logging on to FTP server please check the logs for the following:

# tail -f /var/log/messages

Look for this error:

proftpd[11951]: fatal: ScoreboardFile: : unable to use '/var/run/proftpd/scoreboard': No such file or directory on line 74 of '/etc/proftpd.conf'

Check in /var/run for a proftpd folder, if it’s missing you have a bug in your ProFTPd version usually caused by using the Atomic repo to update ProFTPd.

Check for atomic:


# ls -la /etc/yum.repos.d/ | grep atomic
-rw-r--r--.   1 root root   827 May 18  2016 atomic.repo

The solution is to remove the package and reinstall from Plesk repo:


rpm -e --nodeps psa-proftpd
plesk installer --select-release-current --install-component=proftpd
service xinetd restart

Then you should be able to connect again. Please note that any changes to proftpd.conf such as enabling custom PassivePorts will be lost and need to be recreated.

Source: https://community.webcore.cloud/tutorials/plesk_articles/plesk_unable_to_ftp_missing_scoreboard_file_linux/

Symptoms

Webmail webmail.example.com shows the blank page or the default plesk page.

DNS records for webmail.example.com is managed by external DNS server:


# dig +short webmail.example.com @8.8.8.8
203.0.113.2

There is another IP 203.0.113.3 is set in web server configuration file for webmail.example.com:

RHEL-like systems


grep VirtualHost /etc/httpd/conf/plesk.conf.d/webmails/example.com_webmail.conf | grep -v "/VirtualHost"



Debian-like systems


grep VirtualHost /etc/apache2/plesk.conf.d/webmails/example.com_webmail.conf | grep -v "/VirtualHost"



Both IP addresses belongs to the server
Cause

IP address that is set for domain does not match the one specified on registrar’s side.
Resolution

Log into Plesk
Browse to Home > Domains > example.com > Web Hosting Access and change IP address to the correct one 203.0.113.2

If the domain has no hosting and used only to serve mail, Web Hosting Access link is not present in Plesk. However, to update IP for webmail’s configuration file is possible via command line:

Connect to the server using SSH
Update the IP address to correct one:


# plesk bin subscription -u example.com -ip 203.0.113.2

Source: https://support.plesk.com/hc/en-us/articles/115005104213-Webmail-shows-the-blank-page

The Plesk Control Panel has the ability to create multiple MySQL and PostgreSQL databases as well as multiple users within each database. Also, directly accessible via Plesk, are the links to phpMyAdmin and PhpPGAdmin, the PHP interface applications that abstract mysql or postgresql into a web-based administration tool, allowing you to sort, edit, and create tables within a given database.

Before creating your databases within the Plesk Control Panel, please ensure that you have already added a hosted domain name to your dedicated server.

Here is how you can create MySQL (or PostgreSQL) databases using Plesk:
Login to your Plesk Control Panel. The login URL is in the following format (https://ipaddress:8443).
Click on Websites and Domains from the navigation bar on the left.

Select the domain name that you’d like to associate your database with.
Click the Databases icon on the top right menu.

Click the Add Database icon.

Add the Database Name
Select the related site for the data base.
Click the “Create a Database User” box in order to setup database administrator’s credentials.
Enter a username and a password which will be used for accessing the contents of the database.
Select if the User has access to all databases.
Select Access Control for the database.
Click OK.
Now, you can use the phpMyAdmin and other tools where you can manage your database.

I went and adjusted the expected time out to 4 hours on every domain and on the default settings through Plesk. But it seems that instead of time outs being handled by php, the server runs a cron job that handles the timeouts and ignore php settings. That breaks our apps. Is it there a way to change his?

See: https://websavers.ca/plesk-php-sessions-timing-earlier-expected

After switching a WordPress website to FPM served by nginx in Plesk, it fails to load with “404 Not Found” on all pages except start page.

See: https://support.plesk.com/hc/en-us/articles/213912945-A-WordPress-website-on-a-Plesk-server-shows-404-Not-Found-on-all-pages-except-index-php-when-running-on-FPM-by-nginx

For one website

In Plesk, add the content below to the Additional nginx directives field of the WordPress domain at Domains > example.com > Apache & nginx Settings:


    if (!-e $request_filename) {
    set $test P;
    }
    if ($uri !~ ^/(plesk-stat|webstat|webstat-ssl|ftpstat|anon_ftpstat|awstats-icon|internal-nginx-static-location)) {
    set $test "${test}C";
    }
    if ($test = PC) {
    rewrite ^/(.*)$ /index.php?$1;
    }


Install Plesk on Ubuntu. Running the plesk installer results in failure.

Some packages could not be installed. This may mean that you have requested an impossible situation or if you are using the unstable distribution that some required packages have not yet been created or been moved out of Incoming.
The following packages have unmet dependencies:
apache2 : Depends: apache2.2-common (= 2.2.22-13+deb7u3) but it is not going to be installed
apache2-mpm-prefork : Depends: apache2.2-common (= 2.2.22-13+deb7u3) but it is not going to be installed
Depends: apache2.2-bin (= 2.2.22-13+deb7u3) but it is not going to be installed
mysql-server : Depends: mysql-server-5.5 but it is not going to be installed
plesk-base : Depends: sw-engine (>= 2.13.8) but it is not going to be installed
plesk-core : Depends: libcurl3 (>= 7.16.2) but it is not going to be installed
awstats : Depends: perl:any
libapache2-mod-bw : Depends: apache2-api-20120211
libapache2-mod-perl2 : Depends: apache2-api-20120211
Depends: libxslt1.1 (>= 1.1.25) but it is not installable
Depends: libmyodbc but it is not installable
Depends: xsltproc but it is not installable
Depends: libtimedate-perl but it is not installable

or

The apg-get failed with the following message: Reading package lists... Building dependency tree... Reading state information... You might want to run 'apt-get -f install' to correct these: The following packages have unmet dependencies: apache2 :
Depends: apache2-bin (= 2.4.18-2ubuntu3.9) but 2.4.18-2ubuntu3.8 is to be installed
Depends: apache2-data (= 2.4.18-2ubuntu3.9) but 2.4.18-2ubuntu3.8 is to be installed linux-image-virtual:
Depends: linux-image-4.4.0-128-generic but it is not going to be installed plesk-service-node-utilities:
Depends: libidn2-0 (>= 0.6) but it is not going to be installed

Cause
Non-standard repositories enabled in /etc/apt/sources.list file that Plesk is not compatible with, so a system cannot resolve all the dependencies properly.

Resolution
Connect to the server via SSH.

Replace all contents of the file /etc/apt/sources.list with the default content, like below:

Default sources.list for:
Ubuntu 18.04 LTS:

deb http://archive.ubuntu.com/ubuntu bionic main restricted universe
deb http://archive.ubuntu.com/ubuntu bionic-updates main restricted universe
deb http://security.ubuntu.com/ubuntu bionic-security main restricted universe multiverse
deb http://archive.canonical.com/ubuntu bionic partner

Ubuntu 16.04 LTS:

deb http://archive.ubuntu.com/ubuntu xenial main restricted universe
deb http://archive.ubuntu.com/ubuntu xenial-updates main restricted universe
deb http://security.ubuntu.com/ubuntu xenial-security main restricted universe multiverse
deb http://archive.canonical.com/ubuntu xenial partner

Update package lists and install missing dependencies:

apt-get update
# apt-get -f install

Run Plesk installation / update / upgrade.

Source: https://support.plesk.com/hc/en-us/articles/213367169-Unable-to-upgrade-install-Plesk-on-Ubuntu-Debian-the-following-packages-have-unmet-dependencies