refactor: update dependencies

src/smtp.ts

@@ -205,7 +205,7 @@ export class SMTP extends VerifiableTransport {
     const config = {
       ...smtpConfig,
       // deleting undefined properties so the actual config doesn't get overwritten by undefined values
-      ...deleteUndefinedProperties(envConfig),
+      ...(deleteUndefinedProperties(envConfig) as object),
     } as SMTPConfig;
 
     if (typeof config.host === 'undefined') {