Postbox is a relatively new email client for desktop computers running Windows and Mac. It is not free like Thunderbird is actually almost entirely based on the open-source and free Mozilla Thunderbird. If you have been using Thunderbird email client, then perhaps you will struggle to find any differences between Thunderbird and Postbox. The only difference that can be seen is that Postbox uses a different visual theme. The developers have not even bothered to change some of the file names that carry “thunderbird” in part of their names.
As you start using Postbox, you will start noticing the small changes the Postbox developers have made to make it look appealing and to add the ease of using the email client on a large screen desktop computer. The message view pane is no longer near the bottom edge of the window, it is displayed towards the right side of the Postbox window.
You can change the appearance of Postbox by selecting the options from the menubar View → Layout and View → Show. You can switch from the vertical layout to classic layout. You can choose to show or hide the folder pane, focus pane, messages pane, inspector pane and favorites bar.
Postbox makes it easy to send files along with the messages. You can send the files as attachments like people have been doing since ages. For this Postbox makes it very easy for you to browse and select the files right from inside the compose window. But Postbox integrates cloud services like Dropbox, box or OneDrive so that you can include the sharing links of very large files hosted on these cloud services. This makes sending files with the email messages not only very convenient but also makes the files reusable as you can send the same link to many people.
You can download a trial version of Postbox from https://www.postbox-inc.com/.