Jan Štětina

This plugin provides a simple API for storing miscellaneous log entries and their overview in admin area (or network 
admin area, if activated on a multisite).
Developed for private use (heavily used by my other plugins), but has perspective for more extensive usage. I can’t guarantee any support in the future nor further development, but it is to be expected. Kindly inform me about bugs, if you find any, or propose new features: <a href="mailto:zaantar@zaantar.eu?subject=[wordpress-logging-service]" rel="nofollow ugc">zaantar@zaantar.eu</a>.
See Usage and FAQ for more information.
<h3>API</h3>
Definitions:
<pre><code>WLS
</code></pre>
<ul>
<li>
should be checked before using any wls function
WLS_VERSION
</li>
<li>
should(!) contain current WLS version string
</li>
<li>
severity levels:
<pre><code>WLS_NOCATEGORY = 0

WLS_INFO = 1

WLS_NOTICE = 2

WLS_WARNING = 3

WLS_ERROR = 4

WLS_FATALERROR = 5
</code></pre>
</li>
</ul>
Functions:
<pre><code>wls_is_registered( $category_name );
</code></pre>
<ul>
<li>
returns <code>true</code>, if <code>$category_name</code> is registered
wls_register( $category_name, $description );
</li>
<li>
registers <code>$category_name</code> as a log category.
</li>
<li>
<code>$description</code> will be shown in admin area
wls_clear( $category_name );
</li>
<li>
deletes all log entries of category $category_name
wls_unregister( $category_name );
</li>
<li>
same as wls_clear & removes category $category_name from the list
wls_log( $category_name, $text, $user_id, $date, $blog_id, $severity = 0 );
</li>
<li>
inserts a new log entry into specified category
</li>
<li><code>$date</code> must be formated according to ISO 8601</li>
<li>
<code>$severity</code> should be one of defined severity levels (see above)
wls_simple_log( $log_name, $text, $severity = 0 );
</li>
<li>
equivalent to <code>wls_log( $category_name, $text, get_current_user_id(), date( 'c' ), get_current_blog_id(), $severity);</code>
</li>
</ul>

WordPress Logging Service

Provides a simple API for storing miscellaneous log entries and their overview in admin area.

PhilHilton

This plugin is not affiliated with WP Forms, makers of the WP Mail SMTP plugin. Please do not bother them with support requests. It is a 3rd party solution to the lack of logging in the free version of their product.
Please bear in mind that future updates to WP Mail SMTP may break this plugin’s ability to log messages, and it may take some time for an update to be released. If they go out of their way to remove the WordPress Action Hook it depends on then an update may not be possible at all. Please use this plugin at your own risk.
This plugin has only been tested with the SMTP configuration, and not any of the other implementations provided by WP Mail SMTP. If you use it with another configuration I would be interested in hearing about you experience so that I can either confirm here that it works or make changes so that it will.

Logger for WP Mail SMTP (3rd Party)

This plugin is not affiliated with WP Forms, makers of the WP Mail SMTP plugin. Please do not bother them with support requests.

WordPress Logging Service vs Logger for WP Mail SMTP (3rd Party)