I have been trying to send email for registration, invitations and so on.
On local development, emails get sent. However once on the server no mails arrive.
I installed postfix. I was trying to setup a mail server but gave up. So currently, If I type in terminal
peter# mail firstname.lastname@example.org
$res = mail('email@example.com', 'subj', 'bodddd');
According to your comment above, it looks like your sendmail path is either wrong or commented out in your php.ini. It should be something like this:
sendmail_path = /usr/sbin/sendmail -t -i
If you're unsure where your sendmail binary resides, you may find it by using: