What are some good / feature rich mail clients that support Exchange? I'm a developer at my small office and we exclusively use Exchange 365 for our email, and I am getting incredibly tired and frustrated of the web interface. I would like to use a local mail client.

Postbox looked great, but some research reveals it does not natively support Exchange. I would like to have a client similarly feature rich (particularly when it comes to tagging/organization), but natively supports Exchange protocols.

Any recommendations?
I'll state the obvious one: Outlook:Mac supports Exchange natively, including support for Exchange's categories (which Exchange uses instead of tags)

There are third-party add-ins like MailTags which add support for categories/tags to Apple Mail.

Thunderbird + ExQuilla doesn't support categories/tags.