I don't know if it would still hold true since there seems to have been a major 'change' in LMT, but a couple of years ago I had a problem with my LMT ordering. In order to straighten it out, I did a 3-way call with me, LMT Rep, and Disney phone CM. The Disney CM was able to look up my tickets on their system using my credit card number. That was because they were actual Disney tickets, LMT/Tourico was just the 'middleman' in the transaction. These were 'direct to turnstile' tickets, not 'voucher to the ticket booth' tickets. That may make a difference.
I'd suggest that if you are really concerned, call Disney. Have the email & your credit card with you. Disney should be able to tell you if the seller on the email is one of their authorized ticket partners. They may even be able to look up the tickets for you