What's overriding my local_settings.php? I'm using a local_settings.php file, that includes several $conf settings. All of the settings were working as expected until just recently when the mail_system setting started getting overridden somehow.

Now, if I run $ grep mail_system local_settings.php -A2, I get:

$conf['mail_system'] = array(
  'default-system' =&gt; 'DevelMailLog',
);


...yet, the output of $ drush vget mail_system is:

mail_system: Array
(
    [default-system] =&gt; DefaultMailSystem
)


I've always assumed that whatever was defined in the settings.php (or in this case the local_settings.php) would trump the same variable defined elsewhere. I've checked all the other variables I'm setting inside the $conf variable in the local_settings.php and they're set as they are in the file.

Where else might mail_system be getting set that would override the $conf definition?
Enabling the Devel module fixed the issue. Ultimately, I think the issue is specific to the Mail System module and the unusual way it handles settings and defaults.