Problem solved in 1.3.26.33 for me. Thanks to the dev' :-)
With 1.3.26.33 I have also "unread button".
Anyway I thought we were talking about otherwise: a "read button".
I have AM configured for "never" mark as read an email. Therefore I'd like to have a "read button".
But that will be another feature request, I guess.
Thanks anyway, great job.
EDIT:
I just saw that in the messages list, when I select a message, a button appears: "mark as read" if the message is unread, and "mark as unread" if the message is read. And both of them if I select a message read and another unread.
That would be perfect for the window message.