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

ts/mail/delivery/classes.smtp.client.legacy.ts

@@ -841,34 +841,29 @@ export class SmtpClient {
     if (!this.options.dkim?.enabled || !this.options.dkim?.privateKey) {
       return;
     }
-    
+
     try {
       logger.log('debug', `Signing email with DKIM for domain ${this.options.dkim.domain}`);
-      
+
       // Format email for DKIM signing
       const { dkimSign } = plugins;
       const emailContent = await this.getFormattedEmail(email);
-      
-      // Sign email
-      const signOptions = {
-        domainName: this.options.dkim.domain,
-        keySelector: this.options.dkim.selector,
+
+      // Sign email with updated mailauth API
+      const signResult = await dkimSign(emailContent, {
+        signingDomain: this.options.dkim.domain,
+        selector: this.options.dkim.selector,
         privateKey: this.options.dkim.privateKey,
-        headerFieldNames: this.options.dkim.headers || [
+        headerList: this.options.dkim.headers || [
           'from', 'to', 'subject', 'date', 'message-id'
         ]
-      };
-      
-      const signedEmail = await dkimSign(emailContent, signOptions);
-      
-      // Replace headers in original email
-      const dkimHeader = signedEmail.substring(0, signedEmail.indexOf('\r\n\r\n')).split('\r\n')
-        .find(line => line.startsWith('DKIM-Signature: '));
-      
-      if (dkimHeader) {
-        email.addHeader('DKIM-Signature', dkimHeader.substring('DKIM-Signature: '.length));
+      });
+
+      // Add DKIM-Signature header to email
+      if (signResult.signatures) {
+        email.addHeader('DKIM-Signature', signResult.signatures);
       }
-      
+
       logger.log('debug', 'DKIM signature applied successfully');
     } catch (error) {
       logger.log('error', `Failed to apply DKIM signature: ${error.message}`);