In the case that you’re not ready to leave Gmail you can setup a forward in your Zoho settings. Click on Control Panel, User Details and then Mail Accounts and you’ll see Mail Forwarding.
The above will cover your inbound, but to send email you’ll need to setup the “send mail as” option in Gmail. You can find the Zoho SMTP settings here.
Even though there might not be much reason to do so, I decided to leave Gmail since 90% of my mail was coming in via other domains anyway.
So far I’m digging Mailbird, but if you need something more powerful you might check out eM Client.
Update: 30 Oct 2014: Well, that didn’t even last a week. I’ve been using Gmail since 2004. All my mail since then is stored there. Their calender and contacts and general interface are superior to anything I’ve found yet. I’d still like to move away from Google, but at least for now, Mailbird isn’t it. If you know of any mail clients that have a great design, come with an import option and have a calendar and contacts feature, please get in touch.
Update: September 2015: Since writing this article almost a year ago, I’ve moved to Linux as my primary OS. When I made the move I looked for email clients that would work with Linux and found Geary. It’s very similar to Mailbird. You’ll need to allow “less secure apps” in your Google account if you wish to connect it. There’s also a program called RainLoop, which is a little more robust even if the setup is a little more involved.
Lastly, let’s make sure you’re emails aren’t going to SPAM by setting up Sender Policy Framework. You can find the Zoho portion of the instructions here and the CloudFlare part of the instructions here.
Here’s what mine looks like: