14. Mail services

Univention Corporate Server (UCS) provides mail services that users can access via standard mail clients such as Thunderbird.

Postfix is used for sending and receiving mails. In the basic installation, a configuration equipped for local mail delivery is set up on every UCS system. In this configuration, Postfix only accepts mails from the local server and they can also only be delivered to local system users.

The installation of the mail server component implements a complete mail transport via SMTP (see Installation). Postfix is reconfigured during the installation of the component so that a validity test in the form of a search in the LDAP directory is performed for incoming emails. That means that emails are only accepted for email addresses defined in the LDAP directory or via an alias.

The IMAP service Dovecot is also installed on the system along with the mail server component. It provides email accounts for the domain users and offers corresponding interfaces for access via email clients. Dovecot is preconfigured for the fetching of emails via IMAP and POP3. Access via POP3 can be deactivated by setting the Univention Configuration Registry Variable mail/dovecot/pop3 to no. The same applies to IMAP and the Univention Configuration Registry Variable mail/dovecot/imap. The further configuration of the mail server is performed via Univention Configuration Registry, as well, see Configuration of the mail server.

The management of the user data of the mail server (e.g., email addresses or mailing list) is performed via UMC modules and is documented in Management of the mail server data. User data are stored in LDAP. The authentication is performed using a user’s primary email address, i.e., it must be entered as the username in mail clients. As soon as a primary email address is assigned to a user in the LDAP directory, a listener module creates an IMAP mailbox on the mail home server. By specifying the mail home server, user email accounts can be distributed over several mail servers, as well, see Distribution of an installation on several mail servers.

Optionally, emails received via Postfix can be checked for spam content and viruses before further processing by Dovecot. Spam emails are detected by the classification software SpamAssassin (Spam detection and filtering); ClamAV is used for the detection of viruses and other malware (Identification of viruses and malware).

By default emails to external domains are delivered directly to the responsible SMTP server of that domain. Its location is performed via the resolution of the MX record in the DNS. Mail sending can also be taken over by the relay host, e.g., on the internet provider (see Configuration of a relay host for sending the emails).

The UCS mail system does not offer any groupware functionality such as shared calendars or invitations to appointments. However, there are groupware systems based on UCS which integrate in the UCS management system such as Kopano and Open-Xchange. Further information can be found in the Univention App Center.

Chapter contents:

• 14.1. Installation
• 14.2. Management of the mail server data
  • 14.2.1. Management of mail domains
  • 14.2.2. Assignment of email addresses to users
  • 14.2.3. Management of mailing lists
  • 14.2.4. Management of mail groups
  • 14.2.5. Management of shared IMAP folders
    • 14.2.5.1. Shared IMAP folder - General tab
    • 14.2.5.2. Shared IMAP folder - Access rights tab
  • 14.2.6. Mail quota
• 14.3. Spam detection and filtering
• 14.4. Identification of viruses and malware
• 14.5. Identification of Spam sources with DNS-based Blackhole Lists
• 14.6. Integration of Fetchmail for retrieving mail from external mailboxes
• 14.7. Configuration of the mail server
  • 14.7.1. Configuration of a relay host for sending the emails
  • 14.7.2. Configuration of the maximum mail size
  • 14.7.3. Configuration of a blind carbon copy for mail archiving solutions
  • 14.7.4. Configuration of soft bounces
  • 14.7.5. Configuration of SMTP ports
  • 14.7.6. Configuration of additional checks
  • 14.7.7. Custom Postfix configuration
  • 14.7.8. Configuring the alias expansion limit
  • 14.7.9. Handling of mailboxes during email changes and the deletion of user accounts
  • 14.7.10. Distribution of an installation on several mail servers
  • 14.7.11. Mail storage on NFS
  • 14.7.12. Connection limits
• 14.8. Configuration of mail clients for the mail server
• 14.9. OX Connector