Hi everyone,
We've found an issue with the this beta build wherein attachments added last to a draft are not sent. They are not recognized as a change, therefore not saved in the draft so when it is sent, the last saved state is sent not containing the attachment.
We will address this and the "Recent folders" behavior in the next beta release as soon as we're ready with the bug fix & it has been tested.
Meanwhile, a simple way to avoid the problem is to add your attachments, then make some other change to the draft (i.e. writing in the e-mail body), which will trigger a save.
Martin