present.ts

      const messageParts = [
        `From: ${emailProvider.email}`,
        `To: ${Array.isArray(data.to) ? data.to.join(', ') : data.to}`,
        `Subject: ${encodeHeader(data.subject || '')}`,
        `Date: ${date}`,
        `Message-ID: ${data.messageId}`,
//this is what is causing the error        
 data.references?.length
           ? `References: ${data.references.join(' ')}`
           : null,
         data.inReplyTo ? `In-Reply-To: ${data.inReplyTo}` : null,
        'MIME-Version: 1.0',
        'Content-Type: multipart/alternative; boundary="boundary"',
        '',
        '--boundary',
        'Content-Type: text/plain; charset=utf-8',
        'Content-Transfer-Encoding: 7bit',
        '',
        body,
        '',
        '--boundary',
        'Content-Type: text/html; charset=utf-8',
        'Content-Transfer-Encoding: 7bit',
        '',
        htmlBody,
        '',
      ];