feat(storage): add comprehensive tests for StorageManager with memory, filesystem, and custom function backends

feat(email): implement EmailSendJob class for robust email delivery with retry logic and MX record resolution

feat(mail): restructure mail module exports for simplified access to core and delivery functionalities

ts/mail/routing/classes.dnsmanager.ts

@@ -416,7 +416,7 @@ export class DNSManager {
    */
   public async saveDnsRecommendations(domain: string, records: IDnsRecord[]): Promise<void> {
     try {
-      const filePath = plugins.path.join(paths.dnsRecordsDir, `${domain}.recommendations.tson`);
+      const filePath = plugins.path.join(paths.dnsRecordsDir, `${domain}.recommendations.json`);
       plugins.smartfile.memory.toFsSync(JSON.stringify(records, null, 2), filePath);
       console.log(`DNS recommendations for ${domain} saved to ${filePath}`);
     } catch (error) {