I recommend Zoho mail 110%, I have been using it for years now with minimum to no issues.

I have used Zoho for about four years now, and I was attracted to it by Zoho mail. Zoho mail allows you to have five email addresses with individual mailboxes under one custom domain for free. This is great especially for entrepreneurs and startups, even though you have to purchase the custom domain. The level of functionality is great, it ranks well even when compared to paid services. Another important aspect is that it's not "spammy" and it does not have compromised security. Zoho mail works well, I would recommend it to other business owners and entrepreneurs. It is also continually improving and adding more useful tools such as the MX record checker.

I like Zoho mail's performance and reliability that is enabled by aspects such as adding SPF and DKIM entries in the domain DNS and adjusting MX records. But depending on skill level, these settings could be seen as challenging and could deter some. I found the manual webpage that's available for setting up for a range of domain providers to be quite helpful. There are other sites that cover how to set up Zoho mail, which I also found to be helpful. I realized that it can take long for Zoho mail to pick up added entries to a domain DNS. This is probably split between Zoho mail and a specific domain provider but perhaps some improvements can be done.

Zoho Mail was a very solid experience during the time I used it for over 5 years. It was mostly stable with no major issues whatsoever. The setup was straightforward and I didn't have to switch into the "admin" role during day to day very often. It was quite set-it-and-forget-it for basic email duties. However, as time went on, their email solution and other included goodies felt more and more limited. With everyone using the big names of Gsuite and O365, still being stuck on Zoho's unheard of platform seemed more work than it was worth. It's a great (free under 5 users) product​ if you're not looking to do anything fancy, and only care about basic functionality.

Zoho Mail worked well as a provider for my email on my custom domain. It has all of the features you would need out of a typical email provider, like Gmail​ or Outlook. It was simple to set up, just by adding an MX record into my DNS which took until 5 minutes. The UI is simple but powerful, and their advanced search tools helped me find emails from long ago that I wouldn't be able to find otherwise. Since my only user was myself and an additional service account for miscellaneous sending purposes, I was using the "free" version, which is fully featured, but limited to 5 users. While the free version includes quite a lot of mail features, it is ultimately limited on mail storage, eventually causing me to move away. The free version also included access to some of Zoho's other products, including their contacts and calendar suite (expected with any email provider these days), as well as their office suite (think Word/Excel/Powerpoint). These were nice features to have included, but I ultimately did not use them too much, except for Contacts and Calendar.

Zoho is the underdog in the category of SaaS business suites, competing against GSuite and O365. While the product is fully featured and includes plenty of powerful tools, what it lacks is widespread support and integration, which ultimately made me move to O365, after using Zoho for 5 years. Their propriety storage and document solution are​ basically unheard of compared to Office Online (with OneDrive) and Google Docs (with Drive). Their IMAP/POP3, CalDav, and CardDav solutions are basic and fragmented, though the features are there. Furthermore, with the free account, I didn't get/expect any customer support so any problems were left to myself to fix (not many came up anyways). Primarily, you lack integration with third parties and industry leaders with their services. They don't provide many plugins or connectors to external parties, and when they do, the options are lackluster. Don't expect to be able to automate things with Zoho.

Zoho is definitely okay to use to start with for companies and also if you use emails lightly. But you will feel the difference if you move on to a pro software like Google Workspace. The overall experience needs to be improved in Zoho.

The cost was the main thing I liked about Zoho mail. It was just a dollar per user with limited storage. For startups getting started it is always good to keep the cost low. So zoho did work for us in the first two years. Basically does the work.

The overall user experience is not that great. It looks outdated. Sometimes emails do not sync up well. Also, it is easier to use google login when signing up for services rather than using a custom email. For example, if you are given access to a google doc for your work mail it is really hard to access that document because you do not have an account in google for that mail. Setting up email clients was harder as well with IMAP configurations.

very exciting experience. Especially on Security

Ease of use is the best character of the system

It is generally good in every sense. We use only few services.