PEAR Mail发送UTF-8字符异常求助：SMTP邮件非ASCII字符显示错误

使用PEAR Mail包通过外部SMTP发送联系表单消息，网页采用UTF-8编码，表单变量回显显示正常，但国际字符（čšđž）无法正常发送——收件箱中邮件的Reply-To名称和正文显示异常，邮件头charset为ISO-8859-1。请问这是PEAR Mail还是SMTP服务商的问题？如何修复以在SMTP邮件头和正文中发送非ASCII字符？

相关代码：

//email send
require_once "Mail.php";
require_once "Mail/mime.php";

$from = "<noreply@example.com>";
$to = "<inbox@example.com>";
$subject = "Message from form";
$text = $_POST["body"];

$replyTo = $_POST["senderName"] . " <" . $_POST["senderEmail"] . ">";
$mime = new Mail_mime();
$mime->setTXTBody($text);
$body = $mime->get();

$host = "ssl://mail.censoredsmtpprovider.com";
$port = "465";
// 8465 can also be used.

$username = "censored";
$password = "censored";

$headers = array (
/*'Content-Type' => 'text/plain; charset=UTF-8', TRIED THIS WITH NO EFFECT */
    'From' => $from,
    'Reply-To' => $replyTo,
    'To' => $to,
    'Subject' => $subject);
$headers = $mime->headers($headers);
$smtp = Mail::factory('smtp',
    array ('host' => $host,
        'port' => $port,
        'auth' => true,
        'username' => $username,
        'password' => $password));

$mail = $smtp->send($to, $headers, $body);

我找到一个15年前的可能解决方案，但不确定如今是否仍适用。

问题根源 #

这不是SMTP服务商的问题，是PEAR Mail_mime的默认配置和邮件头编码处理不到位导致的：

• Mail_mime默认使用ISO-8859-1编码生成邮件内容，UTF-8字符会被转码乱码
• 邮件头中的非ASCII字符（比如Reply-To里的用户名）必须按RFC 2047标准编码，直接插入UTF-8字符串会被邮件客户端解析错误

具体修复步骤 #

1. 初始化Mail_mime时指定UTF-8编码
   创建实例时传入编码参数，覆盖默认的ISO-8859-1

2. 编码邮件头中的非ASCII字段
   使用Mail_mime::encodeHeader()方法对包含非ASCII字符的邮件头字段（如Reply-To的名称部分）编码，确保客户端能正确解析

3. 让Mail_mime自动生成正确的Content-Type头
   无需手动添加Content-Type，通过$mime->headers()方法自动生成带UTF-8 charset的头信息

修改后的完整代码 #

//email send
require_once "Mail.php";
require_once "Mail/mime.php";

$from = "<noreply@example.com>";
$to = "<inbox@example.com>";
$subject = "Message from form";
$text = $_POST["body"];

// 对Reply-To中的用户名进行RFC标准编码
$encodedSenderName = Mail_mime::encodeHeader($_POST["senderName"], 'UTF-8');
$replyTo = $encodedSenderName . " <" . $_POST["senderEmail"] . ">";

// 初始化Mail_mime时指定UTF-8编码
$mime = new Mail_mime(array('text_charset' => 'UTF-8', 'html_charset' => 'UTF-8'));
$mime->setTXTBody($text);
$body = $mime->get();

$host = "ssl://mail.censoredsmtpprovider.com";
$port = "465";
// 8465 can also be used.

$username = "censored";
$password = "censored";

$headers = array (
    'From' => $from,
    'Reply-To' => $replyTo,
    'To' => $to,
    'Subject' => $subject);
// 自动生成带UTF-8 charset的邮件头
$headers = $mime->headers($headers);
$smtp = Mail::factory('smtp',
    array ('host' => $host,
        'port' => $port,
        'auth' => true,
        'username' => $username,
        'password' => $password));

$mail = $smtp->send($to, $headers, $body);

关于旧解决方案的说明 #

15年前的解决方案核心思路（指定编码、编码邮件头）仍然适用，因为邮件编码的RFC标准没有本质变化。PEAR Mail虽维护频率低，但核心功能稳定，按规范调整配置即可解决问题。

内容的提问来源于stack exchange，提问作者Lagavulin16