MailScanner fails to start with startup errors matching:
Can't locate Sys/Hostname/Long.pm in @INC (you may need to install the Sys::Hostname::Long module) (@INC contains: /usr/mailscanner/usr/share/MailScanner/perl /usr/mailscanner/usr/share/MailScanner/perl /usr/...el_lib/x86_64-linux-6
If a server is using either of these ConfigServer MailScanner installer/products below, with the listed versions or lower:
MailScanner Installer (msinstall) version 3.17 or lower - https://www.configserver.com/free/mailscanner.html
MailScanner Front-End (MSFE) version 8.28 or lower - https://www.configserver.com/cp/msfe.html
When the server updates to cPanel 86+, MailScanner will not start due to the switch to Perl 5.3.0.
This has been fixed in newer versions of MailScanner and the software should be updated per their instructions here: