Their diligence in resolving whatever issues I've had has been outstanding. Lately it wass a typo in my SPF recoed in advance of the March 15th deadline for email marketing criteria.

it's easy to use in the web, windows app and mobile app

I chose Titan after reviewing many other providers. I had been using the same provider that I bought my domain from for almost 20 years. Then - suddenly - two years of email history disappeared. They were unresponsive but I put off moving until my emails started bouncing from known contacts - one of their servers had been identified as a spammer. I did a lot of research and Titan had the features I needed at a reasonable price. It seemed the best match at the time. Once on, I found it pretty easy to navigate and the customer service is second to none.