Postbox 6.1.6

Postbox

Postbox is a slick, modern-looking email client that provides a rich set of tools to help you get more from your messages. Postbox helps you make the most of your email, offering powerful new ways to find, use, and view email messages and content, organize your work life, and get stuff done.

Postbox features include:

All Your Accounts in One Place -- Postbox Account Groups let's you organize accounts into groups.
Conversations Views — just like Gmail.
Postbox Topics — this takes tagging to a whole new level.
Great Gmail Support — labels, important, send, archive, shortcuts and the calendar!
Cloud File Sharing add-on enables you to send links to your Dropbox, Box, and OneDrive files instead of sending the files themselves.
Responses are pre-canned text/HTML snippets that can be reused within message replies.
Social Media Integration — update your Facebook, Twitter or LinkedIn status as well as auto-import profile photos for prettier email.
RSS and Newsgroup Support
Identities (also known as Aliases)
Date, address, phone number, and package tracking number detection
Full Suite of Keyboard Shortcuts
Anti-Tracking -- To protect your privacy, Postbox 5 has a new Anti-Tracking feature that will alert you when tracking tools are used within a message.
Includes 70 professionally written email responses that anyone can customize and use.
Postbox now includes 25 Beautifully Designed Email Signaturesthat will present you in the best light possible.
Access and manage POP and IMAP email accounts
...and much, much more.

Postbox 6.1.6 changelog:

OmniFocus 3 compatibility
Scrollbar clean up for Dark Mode on macOS
Change to allow searches from contact cards to clear entries in the search bar
Fix to address character encoding regression
Fix for addressing for contacts that contained commas in display names
Fix for an issue that prevented more than one address to be moved across addressing fields
Fix to address contextual menu selection when adding shadows to subsequent images