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Zimbra and Barracuda Cagefight SMTP Address Rejection Battle!

By steve - Posted on 06 May 2011

Ever have your Zimbra server and Barracuda anti-spam system fighting it out over bad recipients? This can really slow down the Barracuda's interface and mail processing.

The fix I used back in 2009 was to make some changes to the POSTCONF settings in

Here's what you do:

  • Open /opt/zimbra/conf/
  • Add or change these config settings:
    • POSTCONF smtpd_reject_unlisted_recipient yes
    • POSTCONF unknown_address_reject_code 550
    • POSTCONF unverified_recipient_reject_code 550
  • Save your changes
  • Restart Zimbra

When you upgrade Zimbra, you'll probably have to add these lines back as some upgrades step on these changes.

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