diff --git a/lib/mailer.service.ts b/lib/mailer.service.ts
index 74aff39d2..de3e2136a 100644
--- a/lib/mailer.service.ts
+++ b/lib/mailer.service.ts
@@ -105,9 +105,11 @@ export class MailerService {
 
   private verifyTransporter(transporter: Transporter, name?: string): void {
     const transporterName = name ? ` '${name}'` : '';
-    transporter.verify()
-      .then(() => this.mailerLogger.debug(`Transporter${transporterName} is ready`))
-      .catch((error) => this.mailerLogger.error(`Error occurred while verifying the transporter${transporterName}: ${error.message}`));
+
+    // wrap value in a promise to ensure then is always defined
+    new Promise(()=>transporter?.verify())
+            .then(() => this.mailerLogger.log(`Transporter${transporterName} is ready`))
+            .catch((error) => this.mailerLogger.log(`Error occurred while verifying the transporter${transporterName}}: ${error.message}`));
   }
 
   public async verifyAllTransporters() {