By that, I mean Excel tables copy as tables, HTML content (mainly tables) copies as HTML tables. It's the only client that has 'real rich text editor' capability. I ultimately settled with MS Outlook for two reasons: All have pros and cons, with my least favorite of the bunch being Spark. I tried MS Outlook, Airmail, Spark, Postbox, and Canary Mail, to name a few. I get a lot of system generated notifications, and I need to keep tabs on a lot of topics/issues. To give context, I average around 250 emails per business day.
I've tried every email client I could get my hands on.