Overview
Outgoing email can use SMTP credentials, Mailgun-compatible HTTP APIs, or OAuth-backed providers depending on what you configure. Settings also control whether Mailgun SMTP applies only to CRM mail or optionally to all WordPress wp_mail when scope is set to site-wide.
Where to configure
Route: #/emails/settings. After saving, send a test message when the UI offers it.
Mailgun and site-wide SMTP
When Mailgun is configured and the sending method is SMTP, you can scope email so CRM-only mail uses the integration—or, when email scope is set to affect all WordPress mail, the plugin registers a phpmailer_init handler so every wp_mail() on the site uses the same SMTP credentials (useful for form plugins and system emails).
Security
Credentials live in WordPress options and are not output to public pages. Updates go through EmailSettingsController with high-privilege CRM capabilities.
Related: Connected services for OAuth mail providers.