Mail attachments are not showing
Since I installed Sierra some attachments in the Mail app are not showing although you can see that a letter has got them.
MacBook Air, macOS Sierra (10.12)
Sierra sometimes omits the last attachment and where there is only one attachment it is always missing.
It only seems to fail if the account is configured for IMAP access. POP access does not have the issue. Best send Apple feedback. Go to http://www.apple.com/feedback/macosx.html and let 'em know.