fix(mail): migrate filesystem helpers to fsUtils, update DKIM and mail APIs, harden SMTP client, and bump dependencies

ts/mail/delivery/classes.delivery.system.ts

@@ -768,19 +768,14 @@ export class MultiModeDeliverySystem extends EventEmitter {
       const rawEmail = email.toRFC822String();
       
       // Sign the email
+      const dkimKeys = await this.emailServer.dkimCreator.readDKIMKeys(domainName);
       const signResult = await plugins.dkimSign(rawEmail, {
+        signingDomain: domainName,
+        selector: keySelector,
+        privateKey: dkimKeys.privateKey,
         canonicalization: 'relaxed/relaxed',
         algorithm: 'rsa-sha256',
         signTime: new Date(),
-        signatureData: [
-          {
-            signingDomain: domainName,
-            selector: keySelector,
-            privateKey: (await this.emailServer.dkimCreator.readDKIMKeys(domainName)).privateKey,
-            algorithm: 'rsa-sha256',
-            canonicalization: 'relaxed/relaxed'
-          }
-        ]
       });
       
       // Add the DKIM-Signature header to the email