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ZAMEEL ISMAIL

I am trying to configure Zoho Mail SMTP in Odoo 18 (Windows 11, local installation) but Odoo fails to send emails even though “Test Connection” is successful.

SMTP settings used:

  • SMTP Server: smtppro.zoho.in

  • Port: 465

  • Encryption: SSL/TLS

  • Username: full Zoho email

  • Password: app password

  • Outgoing email domain: configured

Odoo shows Test Connection: SUCCESS, but when I try to send an actual email (quotation, reset password, etc.) I get:

SMTPServerDisconnected: please run connect() first

What I need help with

  1. What are the correct SMTP settings for Zoho Mail + Odoo 18?

  2. Is there any additional configuration required (SPF, DKIM, ports, app password)?

  3. Why does the Test Connection succeed but real email sending fails?

  4. Does Zoho require a different hostname for SMTP from local servers?

If anyone is using Zoho Mail successfully with Odoo 18, please share the correct working configuration.

Thanks!

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Kunjan Patel

Hello ZAMEEL ISMAIL

I Hope You are doing well,
     
The issue is Odoo's SMTP connection pooling trying to reuse closed connections. Here's the fix:

Create a custom module that forces fresh SMTP connections:
  1. Create module structure:
  mkdir -p custom_addons/mail_smtp_fix/models
  2. Create ir_mail_server.py:
  import logging
  import smtplib
  import time
  from odoo import models, api

  _logger = logging.getLogger(__name__)

  class IrMailServer(models.Model):
      _inherit = 'ir.mail_server'

      @api.model
      def send_email(self, message, mail_server_id=None, smtp_server=None,
                     smtp_port=None, smtp_user=None, smtp_password=None,
                     smtp_encryption=None, smtp_debug=False, smtp_session=None):

          for attempt in range(3):  # 3 retry attempts
              smtp = None
              try:
                  # Always create fresh connection (ignore smtp_session)
                  if mail_server_id:
                      mail_server = self.sudo().browse(mail_server_id)
                      smtp = smtplib.SMTP_SSL(mail_server.smtp_host, mail_server.smtp_port, timeout=30) \
                             if mail_server.smtp_encryption == 'ssl' else \
                             smtplib.SMTP(mail_server.smtp_host, mail_server.smtp_port, timeout=30)

                      if mail_server.smtp_encryption == 'starttls':
                          smtp.starttls()
                      if mail_server.smtp_user:
                          smtp.login(mail_server.smtp_user, mail_server.smtp_pass)
                  else:
                      smtp = smtplib.SMTP_SSL(smtp_server, smtp_port, timeout=30) \
                             if smtp_encryption == 'ssl' else \
                             smtplib.SMTP(smtp_server, smtp_port, timeout=30)
                      if smtp_encryption == 'starttls':
                          smtp.starttls()
                      if smtp_user:
                          smtp.login(smtp_user, smtp_password)

                  smtp.send_message(message)
                  _logger.info('Email sent successfully')
                  smtp.quit()
                  return message['Message-Id']

              except smtplib.SMTPServerDisconnected:
                  _logger.warning(f'SMTP disconnected, retry {attempt + 1}/3')
                  if smtp:
                      try:
                          smtp.quit()
                      except:
                          pass
                  if attempt < 2:
                      time.sleep(2)
                      continue
                  raise
              except Exception as e:
                  _logger.error(f'Email error: {str(e)}')
                  raise
              finally:
                  if smtp:
                      try:
                          smtp.quit()
                      except:
                          pass

  6. Install:
  sudo systemctl restart odoo
  # Then: Apps → Update Apps List → Search "SMTP Connection Fix" → Install

Result: Emails now send successfully with automatic retry logic and fresh connections.

Hope this information helps you.

Thanks & Regards,
Kunjan Patel

ZAMEEL ISMAIL
Author

Hello Kunjan,

Thank you for your detailed explanation and for sharing the custom module fix.

I have implemented the module exactly as described, updated the Apps list, and confirmed that the module is installed. The SMTP Test Connection is successful, but when I try to actually send an email, I still get the same error:

smtplib.SMTPServerDisconnected: please run connect() first

Full traceback shows it failing at:

smtp.send_message(message)
self.ehlo_or_helo_if_needed()
SMTPServerDisconnected: please run connect() first

So even with the forced fresh SMTP connection and retry logic, Odoo 18 on Windows still throws the same “connect() first” error when sending emails (but not during the Test Connection).

It looks like Odoo is still trying to reuse or reinitialize the session incorrectly during the actual send process.

If you have any further suggestions or adjustments for the custom module—especially around handling the EHLO/HELO handshake or explicitly calling connect()—please let me know.

Thanks again for your help.

Kunjan Patel

SOLUTION: 553 Sender Not Allowed to Relay

The 553 error occurs because Zoho only allows sending from the authenticated email address. If Odoo tries to send from a different address (like notifications@yourdomain.com while authenticated as admin@yourdomain.com), Zoho blocks it.

Quick Fix: Set in odoo.conf:
email_from = admin@yourdomain.com
And in Settings → Technical → Email → Outgoing Mail Servers, set Email From Filter = admin@yourdomain.com (must match SMTP username exactly).

Alternative: Add email aliases in Zoho Admin Panel (Users → Email Aliases) to allow sending from sales@, noreply@, etc., then set Email From Filter to *@yourdomain.com in Odoo.

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Kunjan Patel
Best Answer
Hello ZAMEEL ISMAIL
I hope you are doing well,

SOLUTION: 553 Sender Not Allowed to Relay
Quick Fix: Set in odoo.conf:
email_from = admin@yourdomain.com (must match SMTP username exactly).

Hope this information helps you

Thanks & Regards,
Kunjan Patel
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ZAMEEL ISMAIL
Author

Hello Kunjan,

Thanks again for the detailed solution.

The module was installed successfully, and the previous “connect() first” error is gone. But now I'm getting a new error from Zoho:

Unknown error: 553 b'Sender is not allowed to relay emails'

This happens only when sending an email, not during the test connection.

From what I understand, this usually means Zoho is rejecting the message because the From address in Odoo does not match the authenticated Zoho account.

I’m currently using the correct SMTP (smtppro.zoho.in, SSL 465, App Password), so it looks like Zoho is blocking the message based on the sender address.

If you have any guidance on fixing the “553 Sender not allowed to relay” issue specifically with Zoho Pro + Odoo, please let me know.

Thanks.

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LoganMarks
Best Answer

That error usually means Odoo isn’t completing the SMTP handshake before trying to send. With Zoho Mail, the key is using the correct ports and enabling SSL/TLS properly. Make sure you set the SMTP server to smtp.zoho.com, port 465 with SSL or port 587 with TLS, and enter the full email address as the username. Also check that “Less Secure Apps” or “App Passwords” are set correctly in Zoho. Once the connection settings match what Zoho expects, the “please run connect() first” message normally disappears.

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ZAMEEL ISMAIL
Author

Thanks for the suggestion.

We are using smtppro.zoho.in with SSL/TLS on port 465, and the App Password is already generated from Zoho. The Test Connection works successfully, so the SMTP host, port, SSL, and credentials are all valid.

The issue only appears when sending actual emails from Odoo, where it throws:

SMTPServerDisconnected: please run connect() first

So the problem seems to be related to how Odoo handles the SMTP session/handshake during the actual send process, not the Zoho configuration itself.

If there are any additional steps or specific configurations needed for Zoho Pro SMTP, I’d appreciate your guidance.

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Codesphere Tech
Best Answer

Hello,
Please refer this official documentation which is very helpful for you.
https://www.odoo.com/documentation/18.0/applications/general/email_communication/email_servers_outbound.html#using-a-custom-domain-to-send-emails

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ZAMEEL ISMAIL
Author

Thanks for the suggestions.

I have already tried both configurations:

2️⃣ Odoo documentation steps

I followed the official guide as well, including domain configuration.

Still facing the issue

Even though “Test Connection” shows SUCCESS, actual emails fail with:

SMTPServerDisconnected: please run connect() first

This happens for all email actions (quotation, reset password, etc.).

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