Cannot send email from webmail to an external mail server: Error 503 This mail server requires authentication

Created:

2016-11-16 13:02:14 UTC

Modified:

2017-04-24 11:01:55 UTC

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Cannot send email from webmail to an external mail server: Error 503 This mail server requires authentication

Applicable to:

  • Plesk for Windows

Symptoms

The following error appears in MailEnable logs under %plesk_dir%\\Mail Servers\\Mail Enable\\Logging while sending a message using webmail or script to a remote server:

There was an error sending your message: Failed to add recipient: user@example.com [SMTP: Invalid response code received from server (code: 503, response: This mail server requires authentication when attempting to send to a non-local e-mail address. Please check your mail client settings or contact your administrator to verify that the domain or address is defined for this server.)]

Or:

SMTP server response: 503 This mail server requires authentication when attempting to send to a non-local e-mail address. Please check your mail client settings or contact your administrator to verify that the domain or address is defined for this server

Cause

SMTP authentication is required by the remote server. Mail client is not configured to use SMTP authentication on outgoing SMTP server or Smart Host option is enabled.

Resolution

    1. Ensure that Inbound SMTP authentication is not enabled. Open MailEnable snap-ip %plesk_dir%Mail Servers\\Mail Enable\\Bin\\MailEnable.msc and navigate to MailEnable Managment > Servers > localhost > Services and Connectors (or Connectors) > right click on SMTP > Properties > Advanced SMTP > Inbound authentication and select Do not require authentication under Deliveries to local addresses: like is shown below:

SMTP properties 2. Temporarily disable SMTP authentication for local senders:

2.1. Go to MailEnable Managment > Servers > localhost > Services and Connectors (or Connectors) > right click on SMTP > Properties > Relay > Allow Mail Relay and enable Allow relay for local sender address setting.

Note: depends on different versions of MailEnable the path may vary.

2.2. Click Privileged IPs... button, make sure that Denied relay rights parameter is set and add 127.0.0.1 address.

Note : using this configuration in a persistent manner can be a cause of outgoing spam .

3. Make sure that "Smart Host" option is disabled under MailEnable Managment > Servers > localhost > Services and Connectors (or Connectors) > right click on SMTP > Properties > Smart Host . Contact MailEnable support if it is required to setup this option. Plesk does not have such option to setup Smart Host and use it.

Additional information

Configure mail clients to use SMTP authentication. Refer to the following MailEnable KB article .

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