Nylas going "pro" shareware

$7/month is pretty steep for an email client.
https://nylas.com/pricing/

Don't know how many Linux users are going to use it at that price.

that's for professoinal edition with unlimited accounts. For pro edition with unlimited accounts $7 is not bad. There's a free edition too for normal users. I can see the professional edition for enterprises

Still, some of those extras on pro level are surely considered quite useful for basic users.

Also, have a huge preference to one shot deals.
It is annoying to have to renew or upgrade any software, even on a yearly basis, let alone on a monthly one.

I see what you are saying. In that case you should seek alternatives, but I believe their price is OK for enterprise. I think they should rearrange features there though, you are right.

They might want to re-consider their pricing if they want to get on the radar zone:
http://www.tecmint.com/best-email-clients-linux/

yeah, probably

One thing that turned me off...

Had emailed support to ask how to "mark all as read" and instead of getting a personal reply, i got a "nice" subscription to their newsletter.

Not too brilliant.

oh gee!

Did you email them James?
Just received an answer from them:

"...thanks for reaching out. There's not a shortcut for marking everything as read, but if you're using the Gmail shortcut set, you can do `* a` (star, followed by a), to select everything and then mark as read via Shift-I
Cheers—see prefs > shortcuts for more good stuff!"

no, and I'm glad I didn't