PHP implements flow control settings when sending emails

With the development of the Internet, email has become an indispensable communication tool in people's daily lives. Whether it is business emails, personal emails or various notification emails, the volume of emails sent is very large. However, email flow control has always been an important issue in email systems. In order to ensure system reliability, stability and security, mail servers generally limit and control the traffic when sending mails. In PHP email sending, how to set flow control has become a problem that developers need to face. This article will introduce you to the flow control setting method when sending emails in PHP.

1. What is email flow control

Mail flow control refers to limiting and controlling the sending traffic of the email system through certain strategies and algorithms. Traffic in the mail system consists of two parts: the number of messages and the size of the messages. Flow control is designed to ensure the normal operation of the email system and avoid problems such as system crash and data loss caused by sending too many emails. The flow control of the mail system is generally divided into two types: time-based flow control and quantity or size-based flow control.

Time-based traffic control: Traffic control is achieved by limiting the frequency and time interval of sending emails. Most mail servers limit the number of messages sent per minute, hour, or day. For example, a certain mail server only allows 100 emails to be sent per hour, and emails exceeding the limit will be refused to be sent.

Quantity or size-based flow control: Limit the number or size of emails sent. For example, a certain mail server limits the size of each email to no more than 10MB, or each mailbox can only send 50 emails per day.

2. PHP email sending flow control setting method

PHP is a popular web development language and one of the commonly used languages ​​for email sending. In PHP, the implementation of email sending requires the use of the SMTP protocol and SMTP class library. The following uses PHPMailer as an example to introduce the flow control setting method when sending emails in PHP.

1. Time-based flow control

In PHPMailer, we can use the setTimeLimit() function or sleep() function to implement time-based flow control. The code is as follows:

// 设置单个邮件发送时间间隔为1秒
$mail->setTimeLimit(1);

// 设置每发送10封邮件停顿10秒钟
if($i % 10 === 0){
    sleep(10);
}

2. Flow control based on quantity or size

In PHPMailer, we can achieve flow control based on quantity or size by setting the email size or number of emails. The following is an example of PHP code:

// 设置单个邮件大小不能超过10MB
$mail->addStringAttachment(file_get_contents($attachment), $name, 'base64', 'application/octet-stream', 'attachment', true);
if($mail->AttachmentSize() > 10 * 1024 * 1024){
    throw new Exception('Attachment size error.', 400);
}

// 设置每个邮箱每天只能发送50封邮件
if(empty($mailbox['send_times']) || $mailbox['send_times'] < 50){
    // 发送邮件
    $mail->send();
    // 更新发送次数
    $send_times = $mailbox['send_times'] + 1;
    $sql = "UPDATE `email_accounts` SET `send_times` = $send_times WHERE `email` = '".$mailbox['email']."'";
    $db->query($sql);
}else{
    throw new Exception('Emails out of quota.', 400);
}

3. Precautions for flow control settings

1. Set the flow control value reasonably: The flow control setting should be based on the performance and load of the mail server Reasonable settings should be made to prevent the flow control process from being too forced, causing normal email sending to be restricted or excessive traffic impact causing the email system to crash.
2. Refined flow control strategies: Different flow control strategies can be set for different mailboxes and different types of mails. For example, a higher traffic limit can be set for corporate mailboxes, and users’ subscription mails can be sent without setting. Quantity limit, etc.
3. Monitor the flow control situation: Regularly check the effect of the email flow control policy, and make adjustments and modifications according to the actual situation.

4. Summary

Mail flow control is an important part of ensuring the normal operation of the mail system. In PHP email sending, we can use flow control setting methods based on time, quantity or size to control the email sending traffic. Through reasonable flow control strategies, detailed settings and monitoring, the normal operation of the email system can be ensured and problems such as data loss and system crash can be avoided.

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