Humboldt-Universität zu Berlin - Computer and Media Service

Email at HU

The CMS operates its own email infrastructure for HU, which is available to all members of HU and can be used with an HU account. Each HU account has its own mailbox that emails can be delivered to or read from, as well as one or more email addresses through which emails can be received or sent.

The HU mail servers are accessible from the internet, so emails can be retrieved or sent from anywhere in the world. For this, either a client on the end device (e.g., Thunderbird) or the webmailer provided by CMS can be used. The official email address of an HU account is displayed in the account info under the field "Official Address".

 

Best Practices

This section is primarily aimed at "normal" users who receive and write emails via their HU account. However, some points also apply to operators of servers or applications that may automatically send emails.

Use of an email client: Use a desktop client to manage your emails. These are usually more convenient to use and also allow the sending and receiving of encrypted emails.

Signing and encrypting emails: Sign and encrypt your emails with S/MIME. For this, either a desktop client or a corresponding app is required. S/MIME is not supported in the webmailer. Alternatively, PGP can be used, however these methods are not compatible with each other.

Use of the correct email address: The email system at HU is set up so that each HU account can be reached via several different email addresses. Nevertheless, each account has only one official address. This address can be viewed via the account info. When configuring your client, make sure to enter this address as the sender and, if possible, only share this address with your communication partners or publish it on websites.

Some services use only your official address as an assignment to your account. For example, calendar invitations or Zoom invitations do not work correctly if they are addressed to the "wrong" address of an account.

Do not send large attachments: Mailboxes are not file storage. For storing and exchanging files, you can use the HU-Box and then send a link to the storage location or directly share files and folders with other users. This is especially important when sending to many recipients (e.g., via mailing lists), as attachments are stored individually for each recipient.

Do not send mass emails: The HU mail servers do not allow clients to send an unlimited number of emails. This applies, on the one hand, to the number of recipients per email. Additionally, there are restrictions on how many recipients you can address per hour. If the set limits ("rate limits") are exceeded, further emails will be blocked.

If you need to send many emails, please check if a mailing list is suitable for your use case or contact us.

Use meaningful subject lines: Spam and phishing filters work, among other things, based on the subject lines of emails. When writing emails, make sure to choose meaningful and informative subject lines.

Do not send unsolicited emails: Before you write an email to someone, make sure that your counterpart is the right contact for your request. The HU websites are usually well set up and recipients are easy to find.

Store emails in a structured way: Similar to files on your computer or smartphone, emails can be stored in a structured way in folders. For example, a thematic sorting helps you to find emails on a topic more easily. At the same time, dividing your mailbox into several folders relieves your email client.

With very many (e.g., five-digit) emails in one folder, it can happen that the synchronization between mail server and client no longer works properly and, for example, some emails are no longer displayed. Similarly, a structure of hundreds of folders is no longer clear and can also lead to synchronization problems with the email client.

Delete unnecessary emails: Not every email needs to be kept indefinitely. Therefore, regularly delete emails that you no longer need. A good starting point could be, for example, old newsletters, notifications from applications like Moodle, or spam.

Currently, there is no size limit for mailboxes at HU, but we reserve the right to introduce a quota.

Activate spam filter: Emails classified as spam are marked by the mail servers with the header X-Spam-Flag: YES. By activating the spam filter, you can automatically sort these emails into the AutoCleanSpam folder. The classification as spam is independent of measure and also occurs with the spam filter deactivated. Since it can happen that legitimate emails are classified as spam, you should regularly check your spam folder.

Set up server-side email filters: Server-side email filters can be set up via the Forward/Vacation/Filter application to automatically sort emails into different folders of your mailbox based on certain criteria. Unlike client-side filters, these work even when you do not have your client open.

Pay attention to spam/scam/phishing/...: Our mail servers already keep a lot of spam and other unwanted emails away from your mailbox, but they cannot detect everything. Therefore, also pay attention yourself not to fall for scam or phishing. For this, also note our tips on spam and other unwanted emails.

Use of functional accounts: In addition to personal HU accounts, CMS also offers separate functional accounts. Functional accounts should always be used when one or more persons jointly fulfill a specific function (e.g., a secretariat or a support address). Accounts allow, among other things, to send an automatic reply with general information or an expected processing time for the request to all emails. At the same time, the mailbox can be very easily handed over to new employees with previous processes.

 

Information for service/server operators at HU

This section is aimed at all HU members who operate their own IT infrastructure or use service providers outside the HU network and send emails through them. Most points from the best practices also apply in this context.

Local email spooling: If possible, set up a local MTA on your servers that accepts, temporarily stores, and forwards emails from the system and applications. Under Unix-like operating systems, this can be, for example, Postfix or nullmailer. A local spooling MTA ensures that your emails are not lost if you exceed the rate limit once or if emails cannot be forwarded for other reasons.

Use of HU mail servers as relay: You can have emails forwarded/delivered via our servers. If you need to send emails to destination addresses outside the HU, this is required. Please feel free to contact us for this.

Use of meaningful destination addresses: When configuring servers, make sure that automatically generated emails are sent to a meaningful destination address. This can be, for example, your address as the operator.

Also, use a meaningful sender address for automatically generated emails, if possible, so that any replies, but also notifications about delivery problems, reach you. Try to avoid addresses like root@... or www-data@... etc.

Use of mailing lists for newsletters: CMS operates its own mailing list server, which can also be used to send newsletters. If you want to send a newsletter, please set up a mailing list instead of using a commercial solution outside the HU.

No HU senders outside the HU network: With the increasing spread of techniques for securing email traffic, such as SPF and DKIM, HU has also introduced these. SPF and DKIM are used to verify the origin of emails. For sender addresses in the HU domain hu-berlin.de, corresponding information is provided exclusively for the HU mail servers. If you need to send emails from outside the HU network, please contact us and we will advise you on a solution together.

 

Mail servers and services at HU

In the context of email, the actual sending of emails and access to mailboxes must be distinguished. The Simple Mail Transfer Protocol (SMTP) is used for sending emails. The Internet Mail Access Protocol (IMAP) is used for accessing mailboxes. At HU, different servers are responsible for these two aspects:

  • mailhost.cms.hu-berlin.de for sending emails
  • mailbox.cms.hu-berlin.de for mailbox access

The mailbox server provides a uniform access option for all users. The actual mailboxes are stored on several downstream backend servers. In everyday use, the distinction between the backend servers is only important when using mailbox shares.

In addition to the actual email operation, we also provide

  • a webmail application,
  • an interface for managing spam filters, server-side email filters, and out-of-office messages,
  • and our own mailing list service.

 

Structure of emails

Each email consists of two sections: the so-called headers (header as a whole) and the actual email text (body). The header lines (individually also header) contain metadata of an email, such as the sender (From), recipient (To), subject, or information on spam classification. Another component is lines that log the course of the email delivery (Received headers). Normally, each mail server that processes an email adds such a line at the top of the header. If you read the Received headers in reverse order (from bottom to top), you can trace the path an email took to reach the destination mailbox.

By default, header information beyond From, To, and Subject is not displayed by email clients. The full headers are only visible in the source text of emails.

With the exception of information that is only added on the way, all information in the header and body can be freely chosen by the sender. This means that, for example, sender addresses and display names can be easily forged. By using and checking S/MIME signatures, such forgeries can be easily detected.

Analogous to the classic letter, SMTP also distinguishes between the information in the email itself and the address data during delivery. The email is to be seen here as a letter that is sent in an envelope without a window. In addition to From and To, there is therefore an envelope sender (also envelope from) and recipient on the envelope. In many cases, the addresses in the email and in the envelope match, but they can also differ. The distinction between From and Envelope From is particularly important, as this is an important feature for detecting spam or phishing. Both addresses can be viewed: From is displayed as the sender, the Envelope Sender is displayed in the source text of the email in the Return-Path and in the last (thus top-most) Received header.

If you are interested in further information on the topic of email, the article "E-Mail-Header lesen und verstehen" by Thomas Hochstein provides a good introduction.