There are a number of reasons why you might receive a Non Delivery Report:

How to fix – User does not exist

The Non Delivery Report tells you that the user (email address) does not exist.

  • You typed the recipients email address incorrectly – double check the address and resend the email.
  • You have the wrong email address stored in your auto complete cache or address book – this could be because you previously typed the email address incorrectly (and your email program has stored this) or the recipient has a new email address, but your address book or autocomplete cache has the old email address. Update your address book and/or autocomplete cache.
  • You are replying to an email and the reply address contains a typo – contact the recipient (by phone/instant messaging) to find out their correct email address.
  • The recipient may have mail forwarding enabled to an incorrect address. Contact the recipient to check that any forwarding they may have configured is working correctly.

If none of the above issues resolve your problem, contact your email administrator.

How to fix – Unroutable Address

The Non Delivery Report tells you something like: unroutable email / unroutable mail domain / unroutable address

  • You misspelled the domain name when typing the recipients email address. For example you sent your mail to recipient@compny.com instead of recpient@company.com – carefully check the spelling of the address and try sending the message again.
  • The MX records for the recipients domain name are not correctly configured – contact the recipient and suggest they investigate their DNS configuration.

How to fix – Blacklisted IP Address (usually reported by Barracuda)

The Non Delivery Report (NDR) tells you something like: client host [hostname] blocked using Barracuda Reputation 

Your computer’s IP address is almost certainly the one listed on Barracuda’s blacklist – carefully check the NDR – if it has a link to barracuda, the link often contains the IP address which is blacklisted at the end. For example:

554 Service unavailable; Client host [mx.example.dom] blocked using Barracuda Reputation; http://www.barracudanetworks.com/reputation/?r=1&ip=192.168.1.1

If the IP address listed is not within one of the blow IP ranges, the IP is not our responsibility and there is nothing we can do to help. In such cases you have the following options to resolve:

  • Use Webmail to send your email – Webmail does not include your computer’s IP address in the email headers
  • Request that the recipient whitelist you on their Barracuda system
  • Request that your IP address is removed from the Barracuda blacklist

If the IP address is in one of the following ranges, please contact your email administrator who will be able to escalate this issue

  • 217.154.106.x
  • 194.1.164.x
  • 194.1.166.x

Useful Links:

Shortlink: