Shift seems to be the best stand-alone email client. It can integrate multiple accounts, with incoming messages automatically grouped into as many as four categories. Implementation was simple. I just entered the account access information, and it imported everything. I rely on it at work every day, to handle email quickly and efficiently and without losing track of any. It just works. I've never had to call customer support. I've tried other email clients, but Shift is the most reliable and the only one that works for me.

For many years, I had to manage up to 10 email accounts for my clients as an agency owner. That meant having so many open tabs in Chrome and google getting all of the access mixed up. I used to use incognito windows just to keep them separated. Now, with Shift, I have all of these accounts in one place, and each one has its own individual login. Saved me 100's of hours of work. I highly recommend if you have to manage more than 2 in-boxes.

Shift helped me keep all my Google accounts organized and I was a strong proponent of it to keep everything sorted out.