Unibox is dead... do you have any recommendations?

Hi all,

I've been using Unibox for my mac email client for a number of years and love it! It is so easy having all of the email grouped by contact, just like whatsapp. On top of that, one click and there are all the attachments ever sent/received with that contact.

Long story short, it is dead. They aren't supporting it, my licence has been used on too many computers with no way to unlink and they don't respond to any emails (despite still selling on the app store, tut, tut). I've been searching for alternatives with similar functionality but I am having trouble.

Does anyone have any recommendations?

Thanks!