Sending Mail To A Large Number of People - php

Question

I have read lots of questions and answers about this issue on StackOverflow, but none of the ones I've read answered my question specifically.
I do not want to have a mailing list. People tick a box if they want to receive the bulk email. There are no wrong emails because accounts are activated using emails. So no bounce checking. However, I already use PHPMailer (so no issues with headers and such) and add every address to the 'to' field of the email. This means everyone can view all the emails (by reading the email source or hitting "reply to all" in their email client), which will not be desirable by other users. The question is:
1) should I send each email individually, or put all addresses in the 'bcc' field?
2) Won't this make some mailservers mark the email as "spam", no matter how well-structured it is? If so, is there a way to further prevent this (apart from adding the address to some whitelists or setting up domain keys or Unix cron jobs)?
Thanks!
All of the things mentioned here require the user to "subscribe" using a form, and then confirm their email address (like in PHPList). However, I already ask for confirmation when people register, so no sense in asking them again and again. My existing code checks the database; if their "receive-movie-mail" bit is set to 1 (these are gathered using an sql query), an email is sent to them when a new movie is added to the database. So, if you still believe this to be a mailing list (which I think it kind of is, but maybe my definition defies existing software features), I'd like it to have, 1) some way of subscribing users to the list with PHP code (E.G. if the "I want to receive an email every time a movie is uploaded to the database" checkbox is checked, in my form processing code I'll subscribe them), and 2) a way to mail people with PHP (I.E. a function like send_mail_to_list($content) that sends the email to the people I have subscribed, when the "Add Movie" form is submitted). Is there such a mailing list management software?

Answer 1

You should loop over the list of emails and send an individual email for each address:
$mail = new PHPMailer();
$mail->IsSMTP(); // set mailer to use SMTP
$mail->Host = "mail.{domain_name}.com"; // specify main and backup server
$mail->SMTPAuth = true; // turn on SMTP authentication
$mail->Username = "{username}"; // SMTP username
$mail->Password = "{password}"; // SMTP password
$emailFrom = '{email_address}';
$mail->From = $emailFrom;
$mail->IsHTML(true); // set email format to HTML if needed
$emailSubject = '{your subject}';
$emailBody = "Whatever content you are sending.";
$mail->Subject = $emailSubject;
$mail->Body = $emailBody;
foreach($emails => $email) {
$emailTo = $email['email'];
$emailToName = $email['name'];
// send an email to customer
$mail->AddAddress($emailTo, $emailToName);
if(!$mail->Send())
{
echo 'failed';
}
$mail->ClearAddresses();
}

Answer 2

1) should I send each email individually, or put all addresses in the
'bcc' field?
Definitely Individually. Bcc will have your email seen as spam.
2) Won't this make some mailservers mark the email as "spam", no
matter how well-structured it is? If so, is there a way to further
prevent this (apart from adding the address to some whitelists or
setting up domain keys or Unix cron jobs)?
using an SPF record might help. Make sure the reverse-dns to your server is not blacklisted, especially if it's a shared hosting.

Answer 3

I have not done this in php since I know that by default there is no hyper threading in php.
In other languages / frameworks like Ruby or .NET you would send individual emails out together by hyper/multi threading them. This is similar to the *nix cron jobs approach you know of except that it is executed at run time - you create say one thread for every 5 addresses you are sending and then all the threads send out 5 mails one after the other.
Keep in mind that even with this approach the bottle-neck shifts from the application to the mail server you are using. So lets say you are using the inbuilt postgre that ships with apache - it won't handle large volumes since each thread will add load to it.
And of course you should avoid this all together if you can use MailChimp!!

Answer 4

Send each user a separate email, addressed only to them.
Set up DKIM and SPF, or at least create appropriate SPF records. DKIM requires some configuration of the mail server that's actually sending the mail for you, but can help greatly with deliverability, especially to large email providers.

Answer 5

My tip next to others would be: maintain a queue of emails where you can limit delivery rate. Some email providers do not like when you try to deliver thousands of emails to their domain at once.
This should be possible with some MTA's.. But I haven't seen one which is flexible enough to do this. What I used for this was Pear class Mail_Queue + cron job.