Good news! Pop ups are frustrating.

Yes! This is a good news!!!

LOL - I asked about the same thing less than a month ago and got no replies at all ;-)

I'm all for it!

About time. Popups are of the past. Most email services keep it all in line with an option to popup. No worries about popup blockers installed on your browsers in that case. How soon can we see this roll out?

Shivam, popups are not a thing of the past. When we work on PC's we compose multiple messages concurrently while still being able to use other aspects of the interface like Workspaces, File Storage, Calendars etc. 

This is why so many people can't use an iPad and appreciate a PC!

What we are adding in the future is a way to do quick replies from the preview.  This will not be a full compose but provide a way to do a quick response.

Tim Uzzanti, according to your explain the SmaterMail prefers to make a new tab because the user will be able to switch tabs. But for my customer experience, they still need to reply or compose in the single windows. Why not doing the way to implement this feature by setting?

Or just make a simple way to appear popup windows at the center of the screen may be better with low effort.

Completely agree with this!

Can we at least learn from how Gmail does its compose popup? 

As much as I will not use Gmail myself, we have to take our hats off to how they have done an amazing job with their webmail product, and constantly at the front of innovation and good user experience.

A little simplified in-line reply AJAX window would be amazing - or add it as a BETA option for people to try out on SM and report back feedback until you develop it just right for SM :)