I have a Node.js + Express app using Nodemailer.
Email sending works locally with Gmail SMTP, but in production on Render it always times out.

Setup:

• Host: smtp.gmail.com

• Primary port: 465 (secure: true)

• Fallback port: 587 (secure: false, STARTTLS)

• Same credentials and app password as local

• Increased timeouts to 30 seconds

Production logs:
Primary SMTP send failed, retrying on fallback SMTP port: SMTP primary send timeout after 30000ms

Failed to send verification email: Error: SMTP fallback send timeout after 30000ms

My transport setup (simplified):

const transporter = nodemailer.createTransport({
  host: process.env.SMTP_HOST, // smtp.gmail.com
  port: Number(process.env.SMTP_PORT), // 465
  secure: true,
  auth: {
    user: process.env.SMTP_USER,
    pass: process.env.SMTP_PASS,
  },
  connectionTimeout: 30000,
  greetingTimeout: 30000,
  socketTimeout: 30000,
});

Send function:

await transporter.sendMail({  
  from: process.env.MAIL_FROM,  
  to,  
  subject,  
  text,  
  html,  
});

Notes:

App is not serverless; it’s a long-running Render web service.
HTTP endpoints work fine in production.
This seems like only outbound SMTP is failing.
If I use an HTTP email API (Resend), sending works in production.
Question:
Is there anything else to try with Nodemailer/Gmail SMTP in this environment, or is this likely outbound SMTP/network restriction from Render to Gmail (465/587)?
If it’s environment-related, what’s the recommended production approach?