Courier IMAPd and Mail.app warnings

After installing an ISPConfig deployment, everything seemed to work properly, but every now-and-then I got this weird error that there was something wrong with the mail server configuration. The Apple Mail.app showed a exclamation mark with the following message:

The server returned the error: The attempt to read data from the server server.domain.ext failed.

Some research showed that the Apple mail clients tend to open several connections for IMAP, and the default setting of the Courier IMAPd server is to allow (only) 4 connections from the same IP address.

Modifying the Courier config file (/usr/lib/courier-imap/etc/imapd) and allowing e.g. 20 connections from 1 IP address solved this problem.

<ORIGINAL CONFIG>
##NAME: MAXPERIP:0
#
#  Maximum number of connections to accept from the same IP address

MAXPERIP=4

<MODIFIED CONFIG>
##NAME: MAXPERIP:0
#
#  Maximum number of connections to accept from the same IP address

MAXPERIP=20

 If your company / household holds several imap mail clients you may need to increase the counter even more (65536 is the maximum amount of connections for ANY IP address).

If you have SSL enabled on the Courier IMAPd server you also need to add the MAXPERIP variable to the imap-ssl config file (/usr/lib/courier-imap/etc/imapd-ssl).

Finally, you need to restart the Courier IMAPd services (/etc/init.d/courier-imap restart)

Changing SSL Certificates in a ISPConfig v3 Configuration

When you install a Perfect Server based on Centos and ISPConfig v3.x, the system / 'installer' creates for the components self-signed certificates. All these certificates will generate different warnings in your browser, mail clients etc. So time to eliminate those warnings.

First I needed to find out where all those certificates are located, and what there formats are. In my case, there are three services that use SSL/TLS in some form;

1. Postfix SMTP service
2. Courier IMAP service
3. http / Apache2 webservice

Checking the configuration files will reveal their locations.

Click to read more ...

Getting ISPConfig to Work on Centos

This is not a manual describing the installation (pre-requisites) of ISPConfig software on a Centos platform. An excellent manual can be found online. It's just that I ran into a problem when I tried to connect an e-mail client to the (IMAP) mailserver (controled by ISPConfig). All the appropriate ports / listeners were up and running, so it had to be a configuration issue.

Googling around didn't solve my problem. My collegue, Xander (@xmoments / xmoments.nl), cam eto the rescue with the solution;

yum install cyrus-sasl-plain-2.1.23-13.el6.x86_64

Software that handles cleartext passwords between mail processes. After the installation, the mail went flying across the Interwebs.