Roundcube is a free and open source webmail php application. Specifically it is a web IMAP client with well designed user interface. Roundcube being an IMAP client and not a mailserver, it doesnt cater administration thus it doesnt allow user creation and sorts. Roundcube is comparable to a web based solution of Outlook or Thunderbird, and is intended if you already have an internal mail server system and plans to have a online webmail system. Roundcube is still in continious development, though I believe it address the core features an IMAP client provides.
Personal I came to use Roundcube to integrate it with Mandrill and my teams gmail account. Being a casual independent developer, we try our best to minimize cost and resort to free or best valued services as much as possible and mail services are no exception. Previously we use Google App to send emails and promotions under our domain email accounts, but as of the moment email volume ranging only around less than 500 a months isnt worth it for the $5.00 Google App price tag. A short summary of my intergration are based on the following configuration.
1. Create a Mandrill Account, configure your mandrill account and web hooks.
2. Create a PHP application to forward your incoming messages to a target gmail account. For our case I read the 'TO' address from the JSON message from the incoming web hook and forward the message to the target gmail account. This may require a bit of coding but resassure it will be worth it.
3. After your mandrill account is properly setup, and you can forward your messages to your gmail account. You can now configure your Roundcube client.
4. Deploy Roundcube to your server, for our case we use Digital Ocean $5.00 VPS monthly plan.
5. Point your IMAP authentication to Gmail server and your SMTP to Mandrill Server.
6. With this configuration you can read all your messages via Gmail and reply using the Mandrill SMTP server.
This may sound a little bit tedius specially for a small team who just wanted an account that replies using their domain email. In doing this configuration, we were able to a least save a $5.00 monthly subscription and we also plan to configure template email notifications.