I have sent free email links to the buyers who did not receive the purchase email. In one case I had to resend the free link 2-3 times before it was received, but otherwise it worked.
I just now sent a free download link to myself and it arrived within a minute or so and looked fine.
Then I tried to buy a guide through another address and account. Worked fine. Received the link and downloaded, etc.
Not sure what the problem is, but will notify you if the problem continues.