Mail Server

Configuring a mail server is out of scope for this documentation.

Supported SMTP Servers

An SMTP server is used to send and receive email.
Horde can run without an SMTP server. However, many Horde Groupware features require sending email. These include automated calendar event reminders, daily agenda, calendar event invitation, ticket update notification and more.

- Any mainstream SMTP server will work (postfix, exim - most likely even sendmail will do)
- Testing was mostly done against postfix 3.4 - 3.7
- Horde supports TLS and STARTTLS as well as plain connections (unsecure, use only in local networks)

As an alternative, you can submit mail using a sendmail CLI binary.

Supported Mail Filters

You only need a mail filter if you use IMP webmail and the ingo filter application

- Testing was mostly done against dovecot sieve
- Cyrus Sieve and Timsieved are known to work but ancient versions cause trouble
- No testing was done for procmail. There is no obvious reason why it should not work

Supported IMAP Servers

You need no imap server for most horde apps besides IMP webmail

- Any mainstream imap server will work (dovecot, cyrus, courier)
- testing was mostly done against dovecot 2.3
- Horde supports TLS and STARTTLS as well as plain connections (unsecure, use only in local networks)