The main new feature is the Schedule Send feature, and it essentially allows you to schedule emails to be sent at a particular time. The most recent victims: Inbox and Google+, two apps that were once seen as game-changers for their respective fields. Most of Inbox's popular features have now been integrated into Gmail, although this is often not enough for passionate Inbox users.
Spark offers other advanced features as well. At the top you'll find "Scheduled Send". Yes, Inbox Zero is as easy as that with Spark.
What is Spark Mail? Considering it's not a very complex one, we're surprised it took so long for Google to implement it. You now don't have to open a new tab or another app for that matter 'to get things done'. Greetings and common expressions are now much more likely to reflect how you would naturally write them. You can also remove actions from a swipe by choosing the 'No action' option when you're customising it. There's a natural language search and "Smart Notifications" that only alert you about important emails.
Should you use Spark? To schedule email, draft a message on the application. Now, when you're finished writing an email in Gmail, instead of simply hitting the Send button, you'll also have the option to set a specific time for that email to go out, including time suggestions like "tomorrow morning" or "Monday". Spark then automatically sends these emails out to the recipients. At the time of Gmail's launch, Yahoo! Bringing the feature to mobile is expected to make that figure skyrocket. The solution: the sender themselves determines the time at which the mail is to be sent.
Spark Mail tries to be unbelievable at handling notifications. Depends on what you need in an email experience.
First up is a renovation of its Smart Compose feature, a tool used to speed up email composition for an increasingly mobile workforce. However, there isn't a Windows or web version for you to use.