I'm doing some work for a company that's running the corporate version of GMail (not sure of the exact details).
I have a PHP script that sends emails to its employees, using PHPMailer pointed at their Gmail SMTP server.
Depending on values entered on a database using PHP, a person can receive 1, 2 or 3 emails.
If one of these employees is supposed to receive 2 emails, both emails (which are slightly different from another and with different subjects) are sent within milliseconds of each other but only 1 is received by the employee. The emails have only one recipient on each and no BCCs.
If I change the receiving email address to an external address, I receive the correct number of emails.
Does Google have some restriction in place that's preventing
1) multiple emails being sent to the same person from the same email address within a very short space of time
2) multiple emails being received by the same Gmail user from the same email address within a very short space of time?
$mail = new PHPMailer();
$mail->SMTPAuth = true;
$mail->SMTPSecure = 'ssl';
$mail->Host = 'smtp.gmail.com';
$mail->Port = 465;
$mail->Username = $TheEmailUsername;
$mail->Password = $TheEmailPassword;
//Now send it
$mail->Subject = $subject;
$mail->IsHTML(true); //Specify that it is HTML
$mail->Body = $message;