+ Mail Server Configuring a mail server is out of scope for this documentation. ++ Supported SMTP Servers - 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) ++ 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)