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E-mail infrastructure

Through the combination of different products and technologies, we obtain an Open Source-based, modern mail system with high quality virus and spam protection that is both scalable and highly available.

Components

The following products form the building blocks of our powerful e-mail infrastructure:

Guaranteed delivery

Delivery is guaranteed for every e-mail accepted by the mail system. This means that delivery is guaranteed for every e-mail with a destination address on our mail system if they have passed through our test procedure.

The test procedure

E-mail checking takes place via the following steps:

1. SMTP validation

The first step checks that the originating server contains a message that complies with basic features of the SMTP protocol as defined in the standard.

2. Mailbox check

This step checks whether the recipient address is hosted on the mail system and if the message can be delivered locally, or has to be forwarded.

3. Blacklist check

There are various blacklists in which servers known for sending spam are listed.

4. Grey listing

A correctly configured mail server is very error-tolerant when other mail servers have temporary problems, and will accept no e-mails during this time. If this is the case, the originating mail server will then store the e-mail in a temporary storage (queue) and will try to deliver it again at a later time. Grey listing makes use of these circumstances. If an unknown server wants to send an e-mail, it will be rejected at the first attempt with a temporary error. The connection will be allowed at a second attempt.

This technique has proven to be very effective. About 90% of spam e-mails are blocked in this way and therefore do not have to be subjected to the computationally intensive test procedure. You can find more information about grey listing on Wikipedia.

5. Virus and spam scan

In the last step before final acceptance of the e-mail, it is subjected to a virus and spam check. Further test procedures are used in order to classify the e-mail as accurately as possible. The central procedures are:

  • Statistical classification procedure
  • Checks against a number of blacklists
  • Structural check (structure of the e-mail, analysis of the header)
  • Comparison with known word specimens from spam and virus e-mails
  • Checking links that point to phishing or other dangerous websites

Here also, the e-mail receives penalty points for each error. It will be rejected as spam or virus if a specific number of penalty points accrues.

6. Delivery

Once an e-mail has successfully passed through all the checks, it will be delivered. The e-mail is stored in the Inbox or, in the case of forwarding, is sent on to another e-mail address.

E-mail dispatch

In order to prevent the misuse of our e-mail infrastructure, outgoing e-mails are also subjected to a test procedure.

Spam and virus check

All outgoing e-mails are checked for spam and viruses. If the test results are positive, these e-mails will be rejected and therefore will not be sent.

Rate limiting

The dispatch rate for outgoing e-mails is limited to 60 recipients per five minutes for every user. For customers who want to send newsletters, we recommend Newsletter-SMTP-Relay for the unlimited dispatch of e-mails.

Control panel

E-mail accounts, forwarding and settings can be easily and conveniently configured via a web interface. Our resellers can also carry out various white labelling configurations.

Secure call-up and dispatch

E-mails can be called up via POP, IMAP or different Webmails.

All connections are also available in an encrypted form. If you are already a customer and do not yet use an encrypted connection, we would urgently recommend you change to a connection of this kind. Among other things, the encryption prevents your passwords from being intercepted and misused.