We use both sort of / we love our domain level gmail email hosting via our google apps account / we do use the Zimbra client but more to you point in using the entire Zimbra collaboration solution - Zimbra does have some nice feature in that too you can host your self / vs a fully hosted soltuon but as noted too there are unix linux version of zimbra / Cost is also a factor and licencing - matter of personal preference perhaps / we use a mix bag of platforms the google apps domain level email hosting , we also have the office 365 and have a corp domain on hosted exchange and to top all that off / for another venture we have / we use fastmail.com hosted mail services.
I want to jump into this because recently I had to test both for some specific project I was working.
Letís resume it like this. I had the need to create an advanced folder/filtering/tagging system for some log emails. Iím talking about 1000+ emails per day which gets nicely organized into color folders and filtered out based on specific trigger words.
So I started to test Gmail (because storage is free) and a local Zimbra server (not free). The filtering in Gmail is not bad, and the search is very powerful. But then I started to hit into some limitations. So I started to test the rules in Zimbra. Not only I was able to replace the same Gmail rules (while no labels, it has tags which is similar) but I could create far more complex rules. And the search in Zimbra is absolutely phenomenal as well, believe it or not, even while Gmail is from Google, Zimbraís build in search (I think itís using Elastic search) is superb.
I liked how emails are incoming in real time with Gmail but then again, you can also do that with Zimbra. Zimbra has just more features, and if you are talking about business collaboration I think itís the better choice, in particular with the sharing folder and email features which means no more sending emails internally in the same organization.
Gmail is hosted in data center and zimbra you need to host it in your own data center. Features wise, Gmail will be better as it can link to many others platform such as google drive, shared calendar and etc.
Besides that, Office365 also offering a great email system.
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