When I test it, the email messages are simply not delivered (not in spam). But the testing function in Invisioncommunity states test is successful. Approx 70% of users do not receive the system emails (validation email, password reset) though there is no obvious pattern (e.g. it's not like all gmail don't receive it etc. ). This is the same for both SMTP and using Invision Community in the Cloud. It could be something really obvious and simple in the email settings but I cannot spot it.