By mail, do you mean physical mail?
Also, if you are looking for people to bug check for you, it may be good to make a post specifically asking people to quality check your game. For example, you could post here or on reddit to ask for volunteers.
e-mail, I made an e-mail espacially for that...
And I have a beta tester, just one...
I usually make promotion on reddit, do you know any good sub-reddit to looking for volunteers?
lol okay. Usually people only use "mail" to refer to physical mail so I just wanted to double check
sorry, english is not my first language... XD
