Backscatter
Also known as: Blowback, collateral spam
Backscatter is when a mail server sends bounce messages to an innocent third party because their email address was spoofed by a spammer.
Backscatter happens when a spammer sends email using a forged "From" address (spoofing). If the spam message is rejected by a receiving server, that server sends a bounce message (NDR) back to the address listed in the "From" field.
Since the "From" address belongs to an innocent victim, not the spammer, the victim receives a flood of confusing bounce notifications for emails they never sent. This is called backscatter.
To prevent your domain from generating backscatter, configure your mail server to reject invalid recipients during the initial SMTP conversation (at the "RCPT TO" stage) rather than accepting the message and bouncing it later.
Related Terms
Bounce (Soft)
A soft bounce is when an email fails to deliver for a temporary reason, like a full inbox or a short outage at the recipient mail server. The address is still valid, and the email may be delivered if you try again later.
Learn more →Email Appending
Email appending is when you use a third party to add email addresses to your existing customer records based on other details like name or postal address. It is risky because these people did not ask to hear from you, which often leads to spam complaints and poor deliverability.
Learn more →Bounce (Hard)
Hard bounce is when an email cannot be delivered because the address is invalid or blocked. It is a permanent failure and the address should be removed from your list.
Learn more →Shared Server(Shared IP)
A shared server is an email server and IP address that many companies use to send their emails. Your messages go out from the same place as other senders, so you share the same reputation.
Learn more →