Unable to send email from Plesk server using Outlook as mail client: 554 5.7.1: Client host rejected: Access denied

Symptoms

• In an attempt to send an email from Plesk server using Outlook to some external domains (hotmail.com, gmail.com, etc), the following bounce message is returned:

  Server error: '454 4.7.1 [email protected]: Relay access denied'

  ---

  Client host rejected: Access denied: 554 5.7.1 <example.com[203.0.113.2]>: Client host rejected: Access denied

• Other mail clients (Opera Mail, Mozilla Thunderbird) are able to send messages;

Cause

Too restrictive Outlook configuration

Resolution

Note: This article may require additional administrative knowledge to apply. If any help is required, contact the server’s administrator or hosting support.

1. Connect to the server via SSH.

2. Create a backup of the main Postfix configuration file:

   # cp /etc/postfix/main.cf /etc/postfix/main.cf.back

3. Open file /etc/postfix/main.cf using a text editor.

4. Make sure that the row below is present in the /etc/postfix/main.cf or add it if it is missing:

   smtpd_relay_restrictions = permit_mynetworks, permit_sasl_authenticated, defer_unauth_destination

5. Delete or comment (add "#" symbol in the beginning) the below line in the same file:

   #smtpd_sasl_security_options = noplaintext

6. Allow non-secure access by adding the below line:

   smtpd_tls_auth_only = no

7. Reload Postfix with the command:

   # service postfix reload

8. Make sure that Outlook has got the following configuration in Outlook > File > Account Settings > Account Settings > [email protected] > Change.. > More Settings: