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OS X Server: Microsoft Outlook clients might not be able to send mail due to spam filter settings

Symptoms

 Microsoft Outlook users might not be able to connect to an email server on OS X Server if your spam filter is configured in a certain way.

Resolution

Users who use Microsoft Outlook as their email client and who connect to an email server hosted from Mac OS X Server v10.6 or later might not be able to send mail if the spam filter is configured in a certain way. The following (or similar) alert is returned to Outlook clients: 

The message could not be sent because one of the recipients was rejected by the server. The rejected email address was "recipient@example.com" is subject "example", account: "mail.example.com" , server "mail.example.com", protocol: SMTP, server response: "504 5.5.2 < hostname > : Helo command rejected: need fully qualified host name", port: 25, secure (SSL): no, server error: 504, error number: 0x800CCC79.

This issue happens when the OS X Server Mail service (postfix) is configured to require a fully qualified hostname from SMTP clients. This setting is enabled when you turn on spam filtering in Mac OS X Server v10.6 or later.

The fully qualified hostname requirement can be configured separately from other spam filter settings by editing a configuration file. Any modification of a security-related setting should be evaluated prior to making the change.

Once you have evaluated the change, you can use the following steps to implement it. Use these guidelines when editing a configuration file.

For OS X Server (Mountain Lion and later)

  1. In /Library/Server/Mail/Config/postfix/main.cf, locate the smtpd_helo_restrictions setting.
  2. Remove "reject_non_fqdn_helo_hostname" from the list of settings.
  3. Restart the Mail service.

For OS X Lion Server and Mac OS X Server v10.6.x

  1. In /etc/postfix/main.cf, locate the smtpd_helo_restrictions setting.
  2. Remove "reject_non_fqdn_helo_hostname" from the list of settings.
  3. Restart the Mail service.
Important: Information about products not manufactured by Apple is provided for information purposes only and does not constitute Apple’s recommendation or endorsement. Please contact the vendor for additional information.
Last Modified: Oct 22, 2014
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  • Last Modified: Oct 22, 2014
  • Article: TS3023
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