Enable the option to send the emails by Mandrill app https://mandrillapp.com/
Can't see any advantage of implementing a Mandilapp integration into GLPI core. It could be done in a Plugin though
With Mandrill app you can know where is send it the mails from GLPI, who opens, from where it's open, from what device and browser it's open etc. Plus... you can avoid use postfix or another mail server even gmail or MS office 365 etc. This tools it's very usefull and just need a combo box to select [PHPMAIL | smtp | google | mandrill ] and charge their options.... just need change values and Voila! you send mail from events from GLPI like a Boss!
Customer support service by UserEcho