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Email Spoofing


If you are getting returned email that appears to have come from an address you do not have setup,
you may be the victim of email address spoofing.

Email spoofing is the use of someone else’s email address when sending messages. This does not necessarily
mean that someone used your email account. The header information for the email will contain the name of
the server that actually sent the mail. 1&1’s outgoing mail server is moutng.kundenserver.de.

For example, you may get a message saying "Could not deliver message." And when you look at the details, it
appears the mail has come from some_random_name@yourdomain.com. But you do not have this address set up.

How could someone use this to send emails?


The SMTP protocol allows you to specify any email address in the "From:", "Reply To:", and "Errors To" headers.
This is the address that a failed delivery will be returned to.

Will my domain be blacklisted because of this?
The simple answer is, it shouldn’t. Blacklisting is usually done on the server level, not the domain level.
So the mailserver receiving the spam should look at the actual mailserver the mail came from, and blacklist
only that mailserver’s IP address. If you believe your domain is being blacklisted, please contact technical
support, and we will assist you in resolving that issue.

How can I stop this?


The Internet community is currently looking at ways to combat this form of spam. There is currently a proposal
that would add text records (SPF) to a domain’s DNS that will contain the mailservers that are permitted to send
mail from that domain. The incoming mailserver will then reference these records, and either accept the mail or
deny it based on the findings. This will require that both the host of the domain’s DNS and the receiving
mailserver have implemented this protection. Microsoft has a similar proposal known as Sender-ID. It may be
some time before the community as a whole adapts to using these policies.


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