There are other solutions out there Mail-in-a-Box, mailcow, iRedMail, Modoboa and Kopano. However I have been using Zimbra Open Source Edition for a few years now and enjoy the web interface for administration of the system, it makes it easy to add new accounts and alias.

The only thing that I found lacking was the support of ActiveSync, Zimbra does support it but you have to buy their Network Edition and it charges per user which is expensive for home use.

I kept looking for a solution, I stumbled upon Sogo which provides ActiveSync however you would need to setup a Dovecot proxy, I never used Dovecot so I skipped that option. Then I ran into Z-Push, in which they typically use Dovecot or Cyrus IMAP, however I wanted to keep using Zimbra Open Source as my email server, so I found an integration between Zimbra and Z-Push.

What you will need, two Ubuntu 16.04 VMs or Containers

Zimbra Open Source Edition (This assumes you already have Zimbra running)
Z-Push Server

Step 1: Create the files for Z-Push

Create files for Z-Push to write to

mkdir /var/log/z-push

touch /var/log/z-push/z-push.log

chown www-data:www-data -R  /var/log/z-push

Setup logrotate

nano /etc/logrotate.d/z-push

/var/log/z-push/*.log {
daily
missingok
rotate 14
compress
delaycompress
notifempty
}

Step 2: Add Z-Push to system

Add repository to system, update repository, install nginx, php and ensure permissions are set.

sudo nano /etc/apt/sources.list

sudo nano /etc/apt/sources.list
1. deb http://repo.z-hub.io/z-push:/final/Ubuntu_16.04/ /
wget -qO – http://repo.z-hub.io/z-push:/final/Ubuntu_16.04/Release.key | sudo apt-key add –
sudo apt-get update
sudo apt-get install nginx php-7.0 php-7.0-curl
sudo apt-get install zpush-common z-push-config-nginx z-push-autodiscover z-push-ipc-sharedmemory
Ensure z-push has web server permissions

 chown -R www-data:www-data /usr/share/z-push/

Step 3: Download Z-Push Zimbra Backend

Download Zimbra Backend and install script

https://sourceforge.net/projects/zimbrabackend/files/latest/download?source=files
https://sourceforge.net/projects/zimbrabackend/files/Release68/zpzb-install.sh/download

Step 4: Ensure Zimbra DosFilter is updated

Add IP address to whitelist for DosFilter

zmprov mcf zimbraHttpThrottleSafeIPs 10.1.2.3/32

Verify the IP address exists in whitelist

zmprov gs zimbra.example.com zimbraHttpThrottleSafeIPs
zimbraHttpThrottleSafeIPs: 10.1.2.3/32

Step 5: Copy Zimbra Backend files

Copy Zimbra Backend to correct folder and untar

 cp zimbra68.tgz /usr/share/z-push/backend/
./zpzb-install.sh 68
Edit /usr/share/z-push/backend/zimbra/config.php Uncomment the url that fits your needs and update define('ZIMBRA_URL', ' https://zimbra.example.com'); 
Edit /etc/z-push/z-push.conf.php date_default_timezone_set("America/New_York");
define('PROVISIONING', false);
define('BACKEND_PROVIDER', 'BackendZimbra');
define('ZIMBRA_DISABLE_URL_OVERRIDE', true);

Step 6: Configure webserver

Web Server

Enable SSL
Add Certificate and Private Key
Uncomment any PHP-FPM comments
Restart nginx restart

Sample nginx configuration file

server {
server_name zpush.vlarussa.com; # Put your server name
# Uncomment the following lines to enable SSL support if not configured yet
listen 443 ssl;
listen [::]:443 ssl;
listen 1000 ssl;
listen [::]:1000 ssl;
ssl on;
ssl_certificate      /etc/ssl/zpush.vlarussa.com.crt;
ssl_certificate_key  /etc/ssl/private/zpush.vlarussa.com.key;

# If you're using PHP-FPM uncomment the following lines.
include         fastcgi_params;
fastcgi_index   index.php;
fastcgi_param   SCRIPT_FILENAME $document_root$fastcgi_script_name;
fastcgi_param   REQUEST_URI $1;
fastcgi_param   PHP_FLAG "magic_quotes_gpc=off \n register_globals=off \n magic_quotes_runtime=off \n short_open_tag=on";
fastcgi_param   PHP_VALUE "post_max_size=20M \n upload_max_filesize=20M \n max_execution_time=3660";
fastcgi_param   HTTP_PROXY ""; # Mitigate https://httpoxy.org/ vulnerabilities
fastcgi_read_timeout 3660; # Z-Push Ping might run 3600s, but to be safe

location ~* /Microsoft-Server-ActiveSync {
    alias       /usr/share/z-push/index.php;

    access_log  /var/log/nginx/z-push-access.log;
    error_log   /var/log/nginx/z-push-error.log;

    # Attachments ca 15MB max (since binary data needs to be base64 encoded in mine, which results in in about 33% overhead)
    client_max_body_size 20m;
    client_body_buffer_size 128k;

    # Select one of the fastcgi_pass values or adapt to your configuration
    #fastcgi_pass    unix:/var/run/php5-fpm.sock; # for PHP 5.X Debian/Ubuntu
    fastcgi_pass    unix:/var/run/php/php7.0-fpm.sock; # for PHP 7.X Debian/Ubuntu
    #fastcgi_pass    unix:/var/run/php-fpm/php-fpm.sock; # usually RedHat and its derivatives
    #fastcgi_pass    127.0.0.1:9000; # default php-fpm config
}
}

Step 7: Increase PHP-FPM Limits

By default the php-fpm limits are too low (which will cause email fail to deliver or connect) and need to be increased.

nano /etc/php/7.0/fpm/pool.d/www.conf
pm.max_children = 50
pm.start_servers = 15
pm.min_spare_servers = 8
pm.max_spare_servers = 22

sudo service php7.0-fpm restart

Mobile Device Setup

Setup on IOS 11, this is you do not have Autodiscover configured if you would like to simplify adding email accounts see my post on configuring Autodiscover here: Email server Autoconfiguration with Zimbra and Z-Push

Troubleshooting

Verify you get prompted for username/password when you go to https://zimbra.example.com/Microsoft-Server-ActiveSync
Check nginx logs
- ```
/var/log/nginx/z-push-access.log
```
Check Z-Push Logs
- ```
/var/log/z-push/z-push.log
```

Troubleshooting – Zimbra, ensure you have these set

zmprov md zimbra.example.com zimbraPublicServicePort 443
zmprov md zimbra.example.com zimbraPublicServiceProtocol https
zmprov md example.com zimbraPublicServiceHostname zimbra.example.com
zmprov mcf zimbraPublicServiceHostname zimbra.example.com

Restart Zimbra and Web Server

zmcontrol restart

service nginx restart

Optional, If your running your Certificate Authority you will have to install the root CA on the server

Add custom CA-Cert here
- /usr/local/share/ca-certificates/Your-Custom-CA.crt
Update CA Certificates
- sudo dpkg-reconfigure ca-certificates

Zimbra & ActiveSync