[evotz]

I'm looking for an email client (IMAP) that will allow for custom notifications based on the sender.

The only thing I am aware of is Maildroid. But it doesn't work for my particular use (if you select a really long notification sound - say 60 seconds - there's no way to shut it off. It has to play the full 60 seconds).

I'm really shocked that there aren't more per-contact email clients available. Or maybe I'm just not aware of any.

[ManiacJoe]

Most likely the reason few (none?) have that feature is that it requires that the sound for each contact be stored somewhere and the default storage databases so not have a field for such usage.

Obviously an email app can do this implementation, but it is just more work for the devs.
Your best bet would be to find an email app you like then request the feature be added.

[N4Newbie]

Maybe this one? It's Play Store page says "Customizable notifications"

https://www.androidcentral.com/astro-android

[dpw09]

BlackBerry hub

[maildroiddev]

Email us, maybe we can make a change for you.