What is backscatter and how does it work in email?

Email marketer from spamhaus.org explains that backscatter is the result of spam emails using forged 'From' addresses. When these emails bounce, the bounce messages are sent to the forged address, causing innocent users to receive unwanted bounce emails.

Email marketer from web.archive.org (originally Cloudmark) explains that backscatter occurs when spammers forge the sender address on their messages. When these messages bounce due to invalid recipients, the bounce messages are sent to the forged sender address. This creates a problem for the innocent party whose address was spoofed, as they receive a large volume of unwanted bounce messages.

Email marketer from talosintelligence.com explains that backscatter spam is the automatic response from mail servers to forged or non-existent sender addresses used in spam emails. When a spammer sends a message with a fake 'From' address and the email bounces, the bounce message (backscatter) is sent to the unsuspecting victim whose address was forged.

Email marketer from Reddit explains that backscatter is a negative consequence of email spam where innocent users receive bounce messages due to spammers forging sender addresses. This can lead to inbox clutter and potential security risks if the bounce messages contain malicious content or links.

Email marketer from StackExchange explains that backscatter happens when a spammer sends an email with a forged sender address. If the recipient server rejects the email or if the email bounces, a non-delivery report (NDR) is sent to the forged sender address, which is an innocent victim. This results in the victim receiving bounce messages for emails they never sent.

Email marketer from mailchannels.com explains that backscatter is a result of spammers using forged sender addresses. This results in bounce messages being sent to the forged address when the email can't be delivered. This not only floods inboxes, but can also damage a sender's reputation if they are incorrectly identified as the original spammer.

Marketer from Email Geeks explains backscatter is, in simple terms, bounces for email you didn't send (e.g., spoofed email).

Expert from Word to the Wise explains that Backscatter occurs when spam is sent with forged sender addresses, and the non-delivery reports (NDRs) are sent to the forged address, which is not the originator of the spam. This is detrimental for several reasons, including that it indicates a server misconfiguration and a waste of resources.

Expert from Email Geeks explains that the vast majority of mail sent to undeliverable addresses is rejected with a 5xx response at delivery time. However, if an intermediate mail server accepts an email and only later discovers it can’t deliver it, it has to send an asynchronous bounce to the return path. If you fake the return path, the asynchronous bounce sent to a forged email address is backscatter.

Documentation from ietf.org defines backscatter as Non-Delivery Reports (NDRs) or other "bounces" sent to a forged or spoofed address by a mail server. This occurs when a spammer spoofs the sender address, and the receiving server generates a bounce message due to a delivery failure.

Documentation from learn.microsoft.com explains that backscatter storms are the result of spammers using forged sender addresses. When these emails are undeliverable, the receiving mail servers generate non-delivery reports (NDRs) to the forged sender. A large number of these NDRs can flood the recipient's inbox, creating a 'storm' of backscatter.

Documentation from DMARC.org discusses that backscatter occurs when a spammer forges the sender address, and the email bounces because the recipient address is invalid. DMARC helps mitigate backscatter by allowing domain owners to specify how email should be handled if it fails authentication checks, reducing the likelihood of forged emails being accepted and subsequently bouncing.

Documentation from proofpoint.com explains that backscatter, also known as collateral spam, occurs when a spammer sends email using a forged or non-existent return address. If the email cannot be delivered, the receiving mail server sends a bounce message to the forged address. The recipient of the bounce message is an innocent bystander who never sent the original email.