Why am I getting spam in my mailbox?

Why do I receive spam?

mailbox (and Heinlein-Support) operate reliable mail servers and spam filters. Almost 20 years of experience as consultants specialized in mail and spam protection systems for many companies and well-known providers help us to recognize what is possible – but also why several large providers do not implement everything. Spam cannot be completely avoided. However, anyone who wants to filter spam successfully must examine certain characteristics or properties of mails and, if necessary, reject them.

On the one hand, there are content-related characteristics, for example:

• the subject line contains “insults”
• the body text contains a link to a website that is known to distribute malware

On the other hand, there are technical characteristics, such as:

• Who is sending this mail?
• How does the sender behave?
• Is it a “normal” mail server or a botnet?
• From which country or location is this mail being sent?

Spam and virus protection at mailbox

Further technical details and configuration options can be found in the article Spam and virus protection at mailbox.

How do we recognize spam?

For a spam filter, it is crucial to recognize whether a message comes from a spammer (or their software). This is, fortunately, quite easy and reliable due to special characteristics and technical features that occur when mails are sent.

At this point, the content of the mail is not of great interest – a mail is not spam simply because the subject line says “Viagra.” Rather, it is spam because it was sent by a spammer with a particular intent.

This distinction is very important to us, because we are convinced that providers must not carry out content-based evaluation or censorship – instead, they must recognize spammers based on their behavior. Spam filtering should therefore only take place when it becomes clear that the mail comes from a spammer.

Responsibility of providers

The problem is that all technical identification features are lost as soon as the first regular mail server has accepted a spam mail. Afterwards, this mail is forwarded from one system to the next and is therefore evaluated as technically unproblematic.
Therefore, the first provider that accepts a mail is always responsible for spam filtering.

The problem with filtering based on content-related characteristics

As soon as a provider has accepted and forwarded a mail, all subsequent providers can only try to limit the damage or “save what can be saved.”

Due to the lost details, filtering based on technical features is no longer reliable for this mail. The only remaining option would therefore be filtering based on content-related characteristics. However, there are several risks involved:

• Aggressive content filtering enormously increases the rate of mistakenly rejected, genuine mails (“false positives”).
• Indirect stigmatization may occur, for example if all “Viagra” mails (including those from doctors and pharmacies) are rejected.
• Content filters process personal content (since they must access the mails).

From these considerations, it becomes clear why we strongly prefer filtering based on technical features and only filter based on content-related features where it is absolutely necessary – in your interest as well as ours.

Spam with Forwarded Mail

If you use a mailbox account but your primary inbox is hosted by another provider – for example Gmail, GMX, web.de, a university, and so on – and you forward all your mail from there to your mailbox inbox, our spam filters must accept a large portion of these messages. All technical characteristics of spam delivery are lost or altered during forwarding. Based on content alone, spam messages that are forwarded in this way can rarely be detected.

Correcting this issue is unfortunately not in our hands at mailbox — please contact your provider. They may simply have overlooked the problem. Also ask why the message was forwarded to mailbox in the first place.

If you operate your mailbox inbox in the slipstream of a forwarding chain, we can no longer guarantee effective spam protection. We repeatedly find that a large share of spam-related complaints concerns messages that were passed through to us via forwarding from other inboxes. In these cases, we will of course continue to do our best to keep your inbox free of junk mail — however, the level of protection against unwanted advertising, phishing, and similar fraud attempts that you are used to (and that is otherwise standard with us) becomes technically impossible.