Geary

★★★★☆

Geary is really lightweight but still feels modern, so it’s a good email client for lower-end hardware. IMAP features are basic, but 90% of what most people will need, most of the time. Plain text email, formatted email, moving messages around, multiple accounts, etc. Comparable to Apple Mail on a Mac, but for Linux.

It’s just email, and assumes you have another application for contacts and calendars. (Think of it in terms of the classic Unix philosophy of using multiple tools, each of which does one thing well.)

Unfortunately there’s still that remaining 10% for which you’ll probably need your mail provider’s web interface or something more complete like Thunderbird, but Geary is plenty for most day-to-day use.

GNOME-ish

Geary is built to run on a GNOME desktop, but it can run just fine on others as long as the services it needs are available. (Folks for contacts, a keyring for passwords, and gnome-online-accounts for some email providers) And if you want to manage your contacts, you’ll need another application for that. I’ve got Geary and GNOME Contacts running quite happily on LXQt without any other GNOME applications.

Though I did have to temporarily install GNOME to configure Gmail access.

More info at Geary.