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Protection against malicious and dubious e-mails: Switching to DFN-MailSupport

As announced in Rector Circular 57/2021, we are using the "DFN-MailSupport" service for the protection of e-mail communication against attachments containing malware, misleading or dangerous content and advertising. For our e-mail users, no changes in e-mail programs are necessary.

Status of the changeover

Since 22.11.2021 all e-mail domains of the TU Chemnitz have been switched to DFN-MailSupport. Since 7.1.2022, all additional e-mail domains that are also supplied by us have also been converted.

Technical background

Until November 2021, all protective measures for e-mail took place on the mail relay servers of the TU Chemnitz.

Previously: Protective measures at the mail relay of the TU Chemnitz.

After the changeover, protection against harmful, misleading, dubious or advertising e-mails will take place on the servers of DFN Mail Support. These servers are distributed redundantly at several locations in Germany.

Changeover: Protective measures at DFN-Mailsupport

Initially, only incoming e-mails will be checked via the DFN Mail Support servers. If harmful or unwanted content is detected, e-mails will not be accepted. E-mails from the TU Chemnitz to the Internet will be checked and sent on the mail relay of the TU Chemnitz until further notice.

Frequently asked questions

The aim of both methods is identical: to prevent harmful, misleading, dubious or advertising e-mails, but not to interfere with normal, desired e-mail exchanges. Many techniques are the same, such as the use of DNS-based blocking lists and established content analysis tools for content analysis (e.g. SpamAssassin).

New functions and changes:

  • Elimination of greylisting (no delay on first email)
  • More anti-virus checks
  • Statistical filters with learning function

With DFN-MailSupport, the previously possible personal freedom of choice of the level of protection (setting in the IdM portal) is omitted in order to ensure a uniformly high level of protection.

As a recipient, you can only see this in the mail headers (in Thunderbird via "More → Show source code" or Ctrl+U). If these lines are there, the email came via DFN-Mailsupport:

Received: from X1551.mx.srv.dfn.de ([194.95.23X.91])
    by XXXX.hrz.tu-chemnitz.de with esmtps  (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 …
X-Virus-Scanned: Debian amavisd-new at mgw2-XXX.srv.dfn.de

With DFN MailSupport, the previously possible personal freedom of choice of the protection level (setting in the IdM portal) no longer applies. For example, detected spam mails are uniformly rejected from a spam score value of 8 points. In delivered e-mails, this value is noted in two header lines:

X-Spam-Score: 7.703
X-Spam-Level: *******

Using the X-Spam-Level: line, you can create an individual filter, e.g. to move e-mails with more than six stars to an extra folder.

With the previous Mail Relay, this header looked somewhat different: X-Spam-Score: 6.7 (++++++) Please note that the concrete spam score values are not comparable, as extended tests are carried out in DFN-MailSupport which increase the values.

Forward such e-mails in full as an attachment to postmaster@tu-chemnitz.de with the subject: Spam. Please read the instructions "Forwarding an e-mail in full" (in German). We use such e-mails to train the filters at DFN-Mailsupport. Please also report e-mails that erroneously receive a high value for X-Spam-Score:.