There is the suggestion on the page to use a caching IMAP proxy. This will cache the connections to the IMAP server for each user, so that not every click in Roundcube on a message leads to the creation of a new connection.

I found these alternatives:

I had a closer look at Nginx IMAP Proxy and Squirrelmail’s IMAP Proxy.

Squirrelmail’s IMAPProxy
This is actually the easiest solution, at least compared to Nginx IMAP Proxy.

Install from EPEL with: yum install up-imapproxy

I have changed the following values in /etc/imapproxy.conf:

server_hostname localhost
listen_port 8143
server_port 143
force_tls yes

To install the service:

service imapproxy start
chkconfig imapproxy on

Roundcube configuration
You need to change the port that Roundcube connects to, instead of port 143 now use 8143 where your Squirrelmail’s IMAP Proxy is running.

In file /etc/roundcubemail/

$config['default_port'] = 8143;

I have added the script to my TBits scripts:

Since the configuration of the Nginx IMAP Proxy is more complicated, I have created a separate post for that: Kolab/Roundcube with Nginx IMAP Proxy on CentOS6

Kolab/Roundcube with Squirrelmail’s IMAPProxy on CentOS6
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