What is domain name spam?
Domain Name Spam is a spamming technique where the sender only knows the domain name and he doesn’t have any valid email address in the domain. The technique involves sending emails to all the possible combinations or to a nicely crafted dictionary. The most common addresses in such a dictionary are:
The generic list is actually very long but I won’t include here all of the addresses.
Other possible entries in the dictionary are common names and different combination of these names. Let’s take for instance the name John Doe. A few possible combinations and the most used are: firstname.lastname@example.org, email@example.com, firstname.lastname@example.org, email@example.com, etc…
What can you do to discourage and stop this kind of spam?
Set up your email server so it will not accept too many emails from the same server within a specified time frame.
Do not send NDR for unknown recipients, this will inform the attacker about the invalidity of those addresses, this is good information for a spammer. The disadvantage with this is that misspells of an address from a legitimate sender will not inform them about the error.
Use less commonly used prefixes for your email addresses.
Instead of “firstname.lastname@example.org” use “email@example.com”.
Instead of “firstname.lastname@example.org” use “email@example.com”.
Instead of “firstname.lastname@example.org” use “email@example.com”.
You do want to still keep your email addresses professional and to make sense to your customers. An email address like Egfa13wge2@yoursite.com will fool domain name spammers, but customers will be tempted to delete the email when they see such an email address in the “To” field of their email.
Also, don’t forget that many domain name spammers hope you have your catch-all turned on. This means that even sending an email to “firstname.lastname@example.org” will end up in the admin’s mailbox even if that email address doesn’t exist. Unless you have a need for your catch-all to be turned on, you should have it turned off by default.