What are reasons causing email bounce

When you send an email it carries the user information of the sender in its header. Headers are attached along with the email and remain attached with it till it reaches its recipient. When the email is forwarded by the recipient the previous header is dropped and the new sender’s information is attached. Headers carry user information like sender’s email address and IP address of the machine from which the email was sent. It also carries information of the hosting server. Understanding the header information is important to know the reasons causing email bounce.

Email Headers:

As stated earlier the email headers carry two IP address one of the local machine it was transmitted from and other of the email host provider. Every recipient server uses blacklist provided by spam monitoring agencies. These spam monitoring agencies monitor the ip’s that spread spam and list them in their database. A continuous check of such ip’s is done until they stop spamming or a de-listing request is received from the ip’s server administrator. The ip is only de-listed after it is confirmed that the ip has stopped spamming.

reasons causing email bounce

Spamhaus Project:

The Spamhaus Project is on such international organization, based in both London and Geneva, founded in 1998 by Steve Linford to track email spammers and spam-related activity.
They maintain four block lists:

  • SBL: Spamhaus Block List maintains a database of IP addresses from which Spamhaus does not recommend accepting email.
  • PBL: Policy Block List maintans database of ip sending unauthenticated email.
  • XBL: Exploits Block List maintains realtime database of IP addresses of hacked systems, infected by 3rd party exploits, worms or viruses and Trojan horse exploits that cause spam.
  • DBL: Domain Block List is a database of the domains which are involved in spamming.

Finding your ip address:

Internet Service Provider (ISP) address: Open Command prompt and type ipconfig /all at the prompt alternatively open google.com and just type my ip and the first line will say “Your public IP address is” where ‘’ is your ip address allotted by ISP.

Email host ip address: ping yourDomainName.com from command prompt and you will get reply from ip address, this is your host ip.

Email and ip Validation:

Ip addresses of the senders are checked with spammers ip database like the one provided by spamhaus. If the Ip’s are found listed in the database of any such provider the email is rejected considering it as a spam. This check also helps in regulating spread of virus, worms and Trojans across the network.

It can be checked if your server ip (web or mail host) is listed in the black list on mxtoolbox.com. If any of your ip is listed kindly contact your ISP or the server administrator depending upon the ip address to get it de-listed.

Thus by following the above procedure you can find the reasons causing email bounce and troubleshoot it.


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