4 star for billing me twice.

Don’t upgrade the app from the free version. If you want to buy the app, delete the free version and buy the pro version. I was billed twice when i tried to download the pro version directly.
I first bought from an inapp purchase (from the free app). Then later i had to delete the app and reinstall it. When i downloaded from pro version directly, I was billed again.
This could be a bug from apple. (I might be wrong)
Over all this app is good.

Kzenthil about MailTab for Gmail - Email Client