OpenAtrium + OGM

I was trying to get OGM to work with OA (OpenAtrium) but was unable to do it. mahfiaz was able to work out the following steps for my Ubuntu + OA + exim4 setup. This may help others so I've posted it here. Thanks Mahfiaz :) for the help.

Run: dpkg-reconfigure exim4-config
1a)1) Allow exim4 to recieve mail from wilderness,
click okay until you reach a page saying:
"IP-addresses to listen on for incoming SMTP connections:"
Leave the line blank, you really need to accept emails coming from anywhere.

1b) In the same dialog,
"Split configuration into small files?"
Answer yes. (Actually, I am not sure, if this is required.)

2) admin/og/og_mailinglist
debugging field takes user ID, not username, so it would be just "1" (7.x version uses email address there)

3) Wrote an update to og_mailinglist_exim4_transport.php so it posts
by directly bootstrapping Drupal.
Changed file is /etc/exim4/exim_og_mailinglist/og_mailinglist_exim4_transport.php
I also had to change /etc/exim4/conf.d/transport/95_exim4-config_drupal_og_mailinglist_transport file, group = www-data (was mail), otherwise the og_mailinglist_exim4_transport.php script is not able to read settings.php when bootstrapping Drupal.

Open Atrium restricts access to any page, including example.com/og_mailinglist which was used for posting stuff which comes from mail. With direct posting there is no need for that address anymore (except for the case when someone uses different host). I'll commit the code to module and hopefully one day describe it in the documentation as well. This is generally a good thing, since as bonus it cuts some overhead.

4)
PHP config file, namely /etc/php5/conf.d/pdo.ini
contained an extra line: extension=pdo_mysql.so
which already is present in pdo_mysql.ini and caused the following warning:
"PHP Warning: Module 'pdo_mysql' already loaded in Unknown on line 0"
Not critical, but this pollutes logs and creates confusion.

5)
For Clean URLs to work, I changed Apache configuration
/etc/apache2/sites-enabled/[URL]
in the following block:

AllowOrverride None
to:
AllowOrverride All
And restarted the server: /etc/init.d/apache2 restart
And enabled the Clean URLs from http://[URL]/admin/settings/clean-urls