Basically at the moment, half of the posts summarize that the emails are not being sent to their inboxes or either are not able to send any emails anymore. Sadly, Free Hosting Email Accounts have been removed and require upgrade for usage once again. Sendmail is still possible to be used, but basically emails have been suspended and stopped working due to this topic.
For Mass Emailing, that is basically suspicious activity to be honest, I have no idea why you should ask why was I suspended, besides it being without reason, which would be the time to ask 000webhost or either the Mods on this awesome forum!
Hopefully this summed this stuff up! Just a heads up for all 