Actually, you can send legal/valid checks by email. There are several companies providing this technology. This is one:
Email Check Instantly And Let Them Print Or eDeposit.
I’m not saying your experience was not a scam, but rather email checks are a legal and legitimate way to move a check fast.
However, all checks are subject to fraud. The only way that I know to verify any check is good, is to take the check to a branch of the bank that the funds are drawn on and cash the check there instantly without depositing it—which eliminates the chance of the check bouncing. This is good advice for any paper check also.