When developers want to code and test a mail feature, it's quite risky to use a SMTP server connected to the Internet, but on the other hand it's necessary to check all the process.
There is a really simple way to circumvent that and be sure not to send test emails to real users. The best way is to configure Postfix on developers' computers this way :
In /etc/postfix/main.cf
smtp_generic_maps = regexp:/etc/postfix/generic
In /etc/postfix/generic
/.*/ developer.email@test.com
Reload postfix and voila ! All mail sent by apps in development will be redirected to the developer.