I have installed postfix in Ubuntu as Mail server. But the problem is I am not able to send mail from PHP mail function.
PHP Code
$to = "[email protected]";
$subject = "Test mail";
$message = "Please ignore this e-mail.";
$headers = 'MIME-Version: 1.0' . "\r\n";
$headers .= 'Content-type: text/html; charset=iso-8859-1' . "\r\n";
$headers .= "From: 'xyz'<[email protected]>";
Error log
postfix/pickup[38916]: 10C6B226019C: uid=33 from= postfix/cleanup[38918]: 10C6B226019C: message-id=
<[email protected]> postfix/qmgr[38917]: 10C6B226019C: from=, size=499, nrcpt=1 (queue active) postfix/smtp[38942]: connect to ASPMX.L.GOOGLE.COM[2404:6800:4003:c02::1b]:25: Network is unreachable postfix/smtp[38942]: 10C6B226019C: to=, relay=ASPMX.L.GOOGLE.COM[74.125.68.26]:25, delay=2, delays=0.07/0/1.3/0.62, dsn=5.7.1, status=bounced (host ASPMX.L.GOOGLE.COM[74.125.68.26] said: 550-5.7.1 [111.93.202.110
12] Our system has detected that this message is 550-5.7.1 likely unsolicited mail. To reduce the amount of spam sent to Gmail, 550-5.7.1 this message has been blocked. Please visit 550-5.7.1 https://support.google.com/mail/?p=UnsolicitedMessageError 550 5.7.1 for more information. 17si43634365pfq.99 - gsmtp (in reply to end of DATA command))postfix/cleanup[38923]: 1325D226019D: message-id=<[email protected]> postfix/bounce[38940]: 10C6B226019C: sender non-delivery notification: 1325D226019D postfix/qmgr[38917]: 1325D226019D: from=<>, size=3069, nrcpt=1 (queue active) postfix/qmgr[38917]: 10C6B226019C: removed postfix/local[38937]: 1325D226019D: to=, relay=local, delay=0.08, delays=0.04/0/0/0.04, dsn=2.0.0, status=sent (delivered to command: procmail -a "$EXTENSION") postfix/qmgr[38917]: 1325D226019D: removed
It looks like gmail is marking it as spam and dropping it, and one of the posibles reasons can be because he can't trust your server.
You can try to establish a reverse DNS and maybe if the gmail servers can resolve a DNS lookup, they would'nt discard the message from your server.
In this article you can read a guide about configuring a postfix server to send messages with gmail.