I am very happy with the app even though there are a few minor problems.

I have switched from Thunderbird to Airmail 3 and am really pleased with the way it works.
I use filtering to automatically move things to my iMap folders, which seems to be working OK.
But If you create a filter and apply the filter, it does not remove the item from the inbox until you close it and open the inbox again.
In the iOS version, when you type V to move things it could use some options to bring up a move to the last one again.
And it would be nice if you could increase the number of items in the list I think it only has 3 now for the last items filtered.

Sometime when you create a new subfolder it hangs and you have to force quit and start up again to get rid of the dialog indication adding a folder.

I cannot find a way to force running the rules after you add a new rule. That would be a necessary addition.

Also it would be nice to be able to send feedback to the developers, which I have not found a way to do.

All in all it was a very good deal for 10 dollars, And I look forward to many years of using Airmail.

Thanks to the developers for a great product.

JimSere about Airmail - Lightning Fast Email, v3.0