Application Logs

Apache Logs

Ubuntu:

/var/log/apache2/access.log OR

/var/log/apache/access.log

CentOS/Redhat/Fedora:

/etc/httpd/logs/access_log

Mysql & Mariadb Logs:

/var/log/mysql/*

SMTP Logs

(Usual locations, but not always the final ones, as different mail servers have their own respective directory)

/var/log/mail.log

/var/log/maillog

/var/log/mail.*

Other applications:

Splunk Logs

Everything is under: /var/log/splunk

Rest details here: Splunk Logs

Fluent Agent logs

var/log/td-agent/td-agent.log

SSM Agent logs

/var/log/amazon/ssm/*

Cloudwatch Agent:

/opt/aws/amazon-cloudwatch-agent/logs/amazon-cloudwatch-agent.log

or /var/log/amazon/amazon-cloudwatch-agent/amazon-cloudwatch-agent.log

Reference: Cloudwatch Logs

Cpanel Logs

Here its detailed: Cpanel Logs

Plesk Logs

Explained here: Plesk Logs