EC2 - Fresh PHP install - Mail not working

This won't directly solve your issue (edit: I mean the error message you have now edited out), but Amazon EC2 instances have a really spotty mail reputation. You're probably going to have deliverability issues.

Thankfully Amazon created the Simple Email Service to go along with EC2, with a free level of service for EC2 customers. The API is pretty simple and there are transport adapters for many excellent PHP mailing libraries, like SwiftMailer (transport).

Please install sendmail extension, I solved this issue just by installing sendmail in my instance.

Just type: sudo apt-get install sendmail in your terminal.

That worked for me