Why do emails sent from nodemailer smtp elastic fall as spam?

Question

I have an API in nodejs where I have configured nodemailer with elastic email smtp. In elastic email I have verified the domain:

export const bookingWelcome = async (req: Request & any, res: Response) => {
    const email = req.body.email;
    const firstName = req.body.firstName;
    console.log(firstName);

    if (email && firstName) {
        const emailSender = new EmailSender();
        console.log(emailSender);
        emailSender.sendEmailProcess("WELCOME", {firstName}, email).then(() => {
            console.log(emailSender);
            return res.status(200).json({success: true});
        }).catch((error) => {
            console.log("Error sending email: ", error);
            return res.status(500).json({error: true, message: "Error sending email"});
        });
    } else {
        return res.status(400).json({error: true, message: "Email and firstName are required"});
    }
  //  console.log(res.);

    // return res.status(200).json({error: false, message: "Email sent"});
};

EmailSender.ts

const transportOptions: any = {
  transport: process.env.ELASTIC_TYPE,
    host: process.env.ELASTIC_SERVER,
    port: process.env.ELASTIC_PORT,
    auth: {
        user: process.env.ELASTIC_USER,
        pass: process.env.ELASTIC_PASS
    }
};

const EMAIL_FROM: any = process.env.emailFrom;
const BRANDING_EMAIL: any = process.env.BRANDING_EMAIL;
const BRANDING_TITLE: any = process.env.BRANDING_TITLE;

const transporter: any = nodemailer.createTransport(transportOptions);




sendEmailProcess(type: EmailTypes, data: any, to: any): Promise<any> {
    try {
      return new Promise((resolve, reject) => {
        const template = this.typesEmail(type);
        this.sendEmailFromTemplate({ to, file: template.template, subject: template.subject, data: { ...data } })
          .then((email) => {
            resolve(email);
          })
          .catch((err: Error) => {
            reject(err);
          });
      });
    } catch (err) {
      reject(err);
    }
  }
}


sendEmailFromTemplate(props: EmailModel): Promise<any> {
    return new Promise((resolve, reject) => {
      try {
        this.brandingEmail = props.brandingEmail || BRANDING_EMAIL;
        this.brandingTitle = props.brandingTitle || BRANDING_TITLE;
        this.from = props.from || this.from;
        this.to = props.to;
        this.bcc = props.bcc;
        this.subject = props.subject;
        this.attachments = props.attachments;
        this.html = props.html;
        this.text = props.text;
        this.file = props.file;
        this.data = props.data;
        this.headers = {
          "isTransactional": "true"
        };
        new Compile()
          .compile({
            file: this.file,
            data: {
              ...this.data,
              from: EMAIL_FROM,
              brandingEmail: this.brandingEmail,
              brandingTitle: this.brandingTitle,
            },
          })
          .then((compile: string) => {
            this.html = compile;
            return this.sendEmail(this);
          })
          .then((response: any) => {
            console.log(response);
            resolve(response);
          })
          .catch((err: Error & any) => {
            console.log(err);
            reject(err);
          });
      } catch (err) {
        console.log(err);
        reject(err);
      }
    });
  }




sendEmail(props: EmailModel): Promise<any> {
    return new Promise((resolve, reject) => {
      try {
        this.from = props.from || this.from;
        this.to = props.to;
        this.bcc = props.bcc;
        this.subject = props.subject;
        this.attachments = props.attachments;
        this.html = props.html;
        this.text = props.text;
        this.headers = {
          "isTransactional": "true"
        };
        transporter
          .sendMail(this)
          .then((emailResponse: any) => {
            resolve(emailResponse);
          })
          .catch((err: Error & any) => {
            reject(err);
          });
      } catch (err) {
        reject(err);
      }
    });

And in the email that I send I am not attaching emojis and much less links, it is pure text and images

But the emails fall into the SPAM folder, whether you send them from gmail or any other. I really do not know what to do or where to communicate so that this does not happen

Header Analyzer

Any advice?

Thanks in advance.