fix(mail): refactor(mail): Remove Mailgun references from PlatformService. Update keywords, error messages, and documentation to use MTA exclusively.

package.json

@@ -1,7 +1,7 @@
 {
   "name": "@serve.zone/platformservice",
   "private": true,
-  "version": "2.8.2",
+  "version": "2.8.3",
   "description": "A multifaceted platform service handling mail, SMS, letter delivery, and AI services.",
   "main": "dist_ts/index.js",
   "typings": "dist_ts/index.d.ts",
@@ -61,7 +61,6 @@
     "mail parsing",
     "DKIM",
     "platform service",
-    "mailgun integration",
     "letterXpress",
     "OpenAI",
     "Anthropic AI",