How about support Yandex.Disk service for storing attachments?
I used to use Airmail integration with my Dropbox. It was awesome and very useful. But now I use Yandex.Disk (https://en.wikipedia.org/wiki/Yandex_Disk) instead Dropbox.
How about Yandex.Disk supoort in the future? They have an API: https://tech.yandex.com/disk/.
Timur Vasyunin shared this idea
also activate send later feature for yandex users
Alexander Kim commented
Agree with Timur. Please, integrate it with AirMail so you'll get more users!