Video: GMail vs Zimbra

Gmail is a free, advertising-supported email service provided by Google. Users may access Gmail as secure webmail, as well via POP3 or IMAP protocols. Gmail's spam filtering features a community-driven system: when any user marks an email as spam, this provides information to help the system identify similar future messages for all Gmail users. Google also provides GMail alternative for business - G Suite Mail.
Zimbra Collaboration Server is an email and calendar server plus much more; think about it like a next-generation Microsoft Exchange server. In addition to email and calendar, it provides file sharing, tasks, contacts, social media, document management and simplified administrative controls all in an award winning webmail user interface built with the latest AJAX web technology. ZCS also provides mobility and syncs to desktop client applications; the server is deployed on commodity Linux and Mac server hardware.
Face to face in the news:

2016 - Gmail for iOS Gets Undo Send button to fight Zimbra

This is the first time in four years Google has updated its iOS app for Gmail. The new version is a lot like the Android version, which has been present on Android devices for the past two years. The new design is the result of customer demand for “highly requested features” like easier message deletion, easier archiving and easier email management, he said.  One of the welcome features is “Undo Send,” which already exists on Google's desktop Inbox service. Undo send gives users a short window of opportunity to recall an email.  Google also improved search and spelling suggestions for terms in search.

2011 - GMail gets instant search to keep up with Zimbra

Quite a strange idea - to make a search plug-in for GMail and Google Apps - i.e. the services of the Search Giant. Nevertheless, the startup CloudMagic had enough courage to make it. And they've created really useful thing. Most people would say that the search in GMail - is great enough, and even if this CloudMagic gives search-as-you-type results - it's not the reason to pay attention to it. But the search speed - is not the greatest feature of CloudMagic. First, it shows search results in a popup widget - on top of the main GMail interface. So if you writing an email and need to find some information in the previous messages or docs - you don't need to save the email to drafts, open the search page, then view the search results one by one, copy something and go back to the email. Now you can (without closing the message) quickly find and copy what you need in the popup widget.

Second, unlike the native GMail search, CloudMagic can search in several Google accounts at once. For example, in your individual GMail account and your work Google Apps account. And it's no need to switch between them. In the settings you just enter your accounts, which should be indexed.

And third, CloudMagic stores its search index on your computer, so you can search your Google Apps even offline! This is quite an easy way to backup your data stored in Google Apps for the case when you don't have an internet connection.

Currently CloudMagic can search in GMail, Google Docs and Google Contacts. But the plans of this startup are much more ambitious. They want to make a universal search engine for all popular online services, including Hotmail, Facebook, Twitter, Yahoo, etc.

Nevertheless, CloudMagic - is still a plugin. And it needs to be installed. For now it supports only Firefox and Chrome.

2010 - GMail signatures for Internet Entrepreneurs - a new advantage over Zimbra

GMail signature
Almost a year ago GMail has become a full-fledged email-service for virtual businesses when it enabled users to send messages from GMail through any SMTP server, i.e. from any email-address (for example, now in your personal GMail inbox you can respond to customer emails and the customer will receive your answer from the corporate domain). However, one little issue prevented this feature of becoming usable - you could create only one signature for all email-accounts. And only a year later that issue was resolved. Now, you can create a separate signature for each email-account in GMail. Moreover, now you can format the signature in WYSIWYG-editor, add links and images to it. Sure that this feature will make Internet entrepreneurs happy.