During checkout, you will be asked to provide an email address. It must be a live email address, because your access key and instructions about how to activate the LearnToMod account will be sent there. If you're buying the subscription for someone else, you have a few options:

Enter their email during the Checkout process, or afterwards, forward the Access Key email to the person you bought it for.

Or here's another option. All LearnToMod users must go to mod.learntomod.com and enter a chosen login email, when activating their LearnToMod account for the first time. The email entered in the Sign Up field doesn't have to be the same email that was entered during Checkout. 

Each LearnToMod account must have a unique email address, so if you're setting up accounts for multiple students, you will need multiple email addresses.