Love the new interface of SmarterMail 16 but a few major items that I've noticed and haven't found a fix for:
1.) The main email window has no way of removing or hiding the preview pane. I am forced to view the small column of all my emails with a large fixed preview pane.
2.) No quick sort for folders/inbox. Before in SmarterMail 15.x I was able to quickly just click the Date, Subject, or From field and have it quickly sort my emails by that option.
3.) You can no longer expand the folder tree in your mailbox without being forced to view emails in each folder as you are expanding. This makes moving emails to folders very cumbersome. Also, once I move the selected email(s) into a folder is completely refreshes my emails and takes me to the top of the page/email list.
4.) I used to be able to add contacts to category (say "VIP") and then when sending emails I could send an email to all contacts in a category, this is no longer the case from what I can see.
5.) Selecting mutliple emails with the Shift + Arrow Keys is buggy. Sometimes it will select the right amount per each arrow press whereas other times it bugs out and selections a much larger section or all emails.
So far those are the major issues I've seen that hopefully get fixed in future releases.