Why are nodemailer letters not coming from the hosting?

Question

Node.js

Tell me why nodemailer letters do not come when the application is hosted, and everything works fine on locallhost, even letters do not get into spam, what could be the problem? I also used the sendgrid platform, everything is the same, the site is hosted on vercel hosting

function sendEmail(message: SendEmailProps) {
  return new Promise((res, rej) => {
    const transporter = nodemailer.createTransport({
      service: 'gmail',
      auth: {
        user: process.env.GOOGLE_USER,
        pass: process.env.GOOGLE_PASSWORD,
      },
    })
    transporter.sendMail(message, function (err, info) {
      if (err) {
        console.log(err)
        rej(err)
      } else {
        console.log(info)
        res(info)
      }
    })
  })
}

export const sendConfirmationEmail = (username: string, email: string, password: string, confirmLink: string) => {
  const message = {
    from: process.env.GOOGLE_USER,
    to: email,
    subject: 'Подтверждение почты',
    html: `
      <h3> Здравствуйте ${username} </h3>
      <p>Чтобы подтвердить ваш email, перейдите: <a target="_" href="${process.env.DOMAIN_NAME}/api/users/activate/${confirmLink}">по этой ссылке</a></p>
      <p>Ваш логин: ${email}</p>
      <p>Ваш пароль: ${password}</p>
    `,
  }

  return sendEmail(message)
}