You can choose either on-premises Exchange installation or Office 365 Cloud. This decision majorly affects the budget allocation in terms of CapEx or OpEx and ownership. Exchange has the facility of owing the corporate licenses and yearly costs are adjustable based on usage. On the other hand, Office 365 has a subscription model, which needs timely payments to utilize licenses. This is a major difference between both models.

The usage of both Exchange and Office 365 Cloud depends on the basis of the organization, each option has its own advantages and disadvantages. In terms of pros and cons, ownership of the Exchange model provides control and independent financial planning. Conversely, with subscriptions, decisions are made regarding expenses and usage. This is very similar to the postpaid and prepaid versions of mobile phones.

Exchange relies on an internet network. In this case, internal communication within the organization functions seamlessly. Employees from the same organization using the same domain remain connected to Exchange and can send and receive emails effortlessly. In the case of downtime or failed internet connection, external emails can't be sent, and incoming external emails can't be received. In the case of Office 365, internet failure affects both internal and external communication. Even within the same organization and office, both internal and external emails cannot be sent or received if the internet connection is disrupted. Even employees from the same office cannot send each other emails.

I have experience with Office 365 and SharePoint.

I have used a webmail service that comes with Plesk for Linux servers.

We had used IBM Notes before but it is an inferior product compared to Exchange.

We switched to Microsoft because Exchange is the most integrated with other Microsoft products.

I have never worked with other similar products. 

I have utilized G Suite. The flexibility that Microsoft has to offer, especially when it comes to email, is better. Sometimes you need the ability to be able to make certain configurations and policy changes that Google might not offer.

I have not used any other similar solution previously. 

We did not use a different solution previously.

We have been using Microsoft Exchange for a long time. Prior to this, we were using a solution called Thunderbird.

I was using Lotus Notes previously to Microsoft Exchange.

Previously, we used Scalix. We switched to Microsoft Exchange for easier integration and better stability. 

I still use Gmail, but I don't use it much. I'm not that impressed. Gmail isn't robust enough. I use the integrated mailbox for iPhone. It's okay but not great. Outlook is the best, but it could be better.

I have not used another solution previously. 

We previously used Google gmail. But,we have a lot of expertise with Exchange. And the thing with Google, or any dormant solution, is that we are a semi-dormant algorithm and we can't have our data out on the cloud.

We've had the same solution for a long time. 

I have not personally worked with other similar solutions.

At the time I joined the organization, they didn't have an email solution in-house. Employees were using their personal emails. Some of were using Yahoo!, some were using Gmail. If someone left the company, they would take with them the emails they had received from clients. We needed an in-house email solution like Exchange so that if someone leaves we are able to keep the emails.

To me, the most important criteria when selecting a vendor are maintenance and support. Features also matter. Then I look at the pricing. Is it too costly, is the organization going to be able to afford it? So cost plays a major role. When I go to the Director and say I want to buy this solution, the main thing he will look at is the pricing. He will ask, "Why are you getting these features, it's very expensive. Why aren't you going with this other option, it's cheaper?" But again, if the support is great and the pricing is a bit higher it's worth it.

I have used Zimbra.

Previously used Lotus Domino and moved to this box of support. We switched because of the help that we easily get from it.