Claws Mail

Why use Claws Mail?  (I'm asking that question in Linux, but it's available for Windows too.) Well, when I looked at email clients that worked on my Debian XFCE installation, I found Thunderbird using 600MB of RAM and Evolution using 300MB. Even GMail open in a browser tab uses 300MB. Claws Mail, on the other hand uses 73MB of RAM:

This would certainly make it useful on an old computer with little memory available, but doesn't it look like some relic from the Windows 95 era? No, it supports GTK3 and at least in Debian some nice themes are available. Still old school but looks OK:

So here is the full list. Why use claws mail?

• Lightweight, low memory usage, but still full featured. Does filtering and processing. Fits in to the XFCE desktop well. In Gnome I use Geary for casual emails and Evolution for more serious use, but Claws does both.
• Supports GTK3 and has a wide range of themes available, from old school to modern.
• Supports OAuth2, the authorisation protocol used by GMail and other email providers now.

There are also some features that Claws Mails does not have that may be reasons not to use it. On the other hand, they may be features you do not need or want:

• Push emails are not a feature. You have to wait until Claws Mail check for new mail, at whatever interval you set.
• New email desktop notifications from GMail don't work because GMail doesn't mark any messages as 'New'. There is a patch available to change behaviour to notify for unread messages, but it involves compiling Claws from source code.
• Emails are displayed by default as plain text, not HTML. There is a plugin to switch to HTML view, but if you prefer the formatting, fonts and background images of HTML mail, Claws is probably not for you.
• Claws Mail doesn't do the modern tiled subject column that Geary does. Layout is strictly old school.

So there you have it, a lightweight, minimal (but still powerful) email client to keep open if you don't like web mail or the size of some other email clients, and are not put off (or in fact enjoy or want) basic email features.