Steps to reproduce:
1. Select PDF file on desktop
2. Hit chosen shortcut to action the selected file
3. Select Email To...
3. Start typing a recipient's name
4. Hit enter for the chosen recipient
5. Hit Alfred's shortcut (nothing happens - it's hung)
Environment notes:
I don't use Mail.app (haven't for many many months), but I noticed that it required a database migration. I did that and tried again. Still an issue. I use Airmail for my default mail client. Late 2013 MacBook Pro Retina 13" running OS X 10.9.3.
Other:
I'm a developer and can provide a spin dump or whatever you need.