Oracle 19c中UTL_SMTP发送邮件空格被截断的问题求助

环境与问题 #

• 数据库：Oracle Database 19c Enterprise Edition Release 19.0.0.0.0 - Production Version 19.20.0.0.0
• 场景：用UTL_SMTP发送HTML格式邮件，能正常收到，但正文里的连续空格（包括前导、尾随）被自动截断，无法保留预期格式。

原代码如下：

declare
 l_mail_conn   UTL_SMTP.connection;
  l_boundary    VARCHAR2(50) := '              =abc1234321cba=';
  p_smtp_host VARCHAR2 (100) := 'smtp.cac.com';
   p_smtp_port      NUMBER := 25;
   p_to VARCHAR2(100) := 'hello@gmail.com';
   p_subject VARCHAR2(100) := 'Hello';
   p_html_msg  VARCHAR2(100) :=  '              ' ||'ABC <br>' || '              ' || 'DEF';
BEGIN
  l_mail_conn := UTL_SMTP.open_connection(p_smtp_host, p_smtp_port);
  UTL_SMTP.helo(l_mail_conn, p_smtp_host);
  UTL_SMTP.mail(l_mail_conn, p_to);
  UTL_SMTP.rcpt(l_mail_conn, p_to);

  UTL_SMTP.open_data(l_mail_conn);
  
  UTL_SMTP.write_data(l_mail_conn, 'Date: ' || TO_CHAR(SYSDATE, 'DD-MON-YYYY HH24:MI:SS') || UTL_TCP.crlf);
  UTL_SMTP.write_data(l_mail_conn, 'To: ' || p_to || UTL_TCP.crlf);
  UTL_SMTP.write_data(l_mail_conn, 'From: ' || p_to || UTL_TCP.crlf);
  UTL_SMTP.write_data(l_mail_conn, 'Subject: ' || p_subject || UTL_TCP.crlf);
  UTL_SMTP.write_data(l_mail_conn, 'MIME-Version: 1.0' || UTL_TCP.crlf);
  UTL_SMTP.write_data(l_mail_conn, 'Content-Type: multipart/alternative; boundary="' || l_boundary || '"' || UTL_TCP.crlf || UTL_TCP.crlf);

  IF p_html_msg IS NOT NULL THEN
    UTL_SMTP.write_data(l_mail_conn, '--' || l_boundary || UTL_TCP.crlf);
    UTL_SMTP.write_data(l_mail_conn, 'Content-Type: text/html; charset="iso-8859-1"' || UTL_TCP.crlf || UTL_TCP.crlf);

    UTL_SMTP.write_data(l_mail_conn, p_html_msg);
    UTL_SMTP.write_data(l_mail_conn, UTL_TCP.crlf || UTL_TCP.crlf);
  END IF;

  UTL_SMTP.write_data(l_mail_conn, '--' || l_boundary || '--' || UTL_TCP.crlf);
  UTL_SMTP.close_data(l_mail_conn);

  UTL_SMTP.quit(l_mail_conn);
END;
/

问题原因 #

这不是UTL_SMTP的问题，是HTML的默认渲染规则：浏览器/邮件客户端会把连续的空白字符（空格、换行、制表符）合并成单个空格，所以你写的连续空格会被自动压缩。

解决方法 #

有两种常用的办法可以保留空格格式：

方法1：使用<pre>标签 #

<pre>标签会保留文本的原始格式，包括空格、换行和缩进，适合需要保留排版的内容。修改p_html_msg的定义：

p_html_msg  VARCHAR2(200) :=  '<pre>' || '              ABC' || '<br>' || '              DEF' || '</pre>';

方法2：用 替换普通空格 #

把每个需要保留的空格替换成HTML空格实体 ，连续空格就用多个 。比如前导的14个空格就写成14个 ：

p_html_msg  VARCHAR2(200) :=  '              ' ||'ABC <br>' || '              ' || 'DEF';

修改后的完整代码示例（以<pre>为例） #

declare
 l_mail_conn   UTL_SMTP.connection;
  l_boundary    VARCHAR2(50) := '              =abc1234321cba=';
  p_smtp_host VARCHAR2 (100) := 'smtp.cac.com';
   p_smtp_port      NUMBER := 25;
   p_to VARCHAR2(100) := 'hello@gmail.com';
   p_subject VARCHAR2(100) := 'Hello';
   -- 使用<pre>标签保留空格格式
   p_html_msg  VARCHAR2(200) :=  '&lt;pre&gt;' || '              ABC' || '&lt;br&gt;' || '              DEF' || '&lt;/pre&gt;';
BEGIN
  l_mail_conn := UTL_SMTP.open_connection(p_smtp_host, p_smtp_port);
  UTL_SMTP.helo(l_mail_conn, p_smtp_host);
  UTL_SMTP.mail(l_mail_conn, p_to);
  UTL_SMTP.rcpt(l_mail_conn, p_to);

  UTL_SMTP.open_data(l_mail_conn);
  
  UTL_SMTP.write_data(l_mail_conn, 'Date: ' || TO_CHAR(SYSDATE, 'DD-MON-YYYY HH24:MI:SS') || UTL_TCP.crlf);
  UTL_SMTP.write_data(l_mail_conn, 'To: ' || p_to || UTL_TCP.crlf);
  UTL_SMTP.write_data(l_mail_conn, 'From: ' || p_to || UTL_TCP.crlf);
  UTL_SMTP.write_data(l_mail_conn, 'Subject: ' || p_subject || UTL_TCP.crlf);
  UTL_SMTP.write_data(l_mail_conn, 'MIME-Version: 1.0' || UTL_TCP.crlf);
  UTL_SMTP.write_data(l_mail_conn, 'Content-Type: multipart/alternative; boundary=&quot;' || l_boundary || '&quot;' || UTL_TCP.crlf || UTL_TCP.crlf);

  IF p_html_msg IS NOT NULL THEN
    UTL_SMTP.write_data(l_mail_conn, '--' || l_boundary || UTL_TCP.crlf);
    UTL_SMTP.write_data(l_mail_conn, 'Content-Type: text/html; charset=&quot;iso-8859-1&quot;' || UTL_TCP.crlf || UTL_TCP.crlf);

    UTL_SMTP.write_data(l_mail_conn, p_html_msg);
    UTL_SMTP.write_data(l_mail_conn, UTL_TCP.crlf || UTL_TCP.crlf);
  END IF;

  UTL_SMTP.write_data(l_mail_conn, '--' || l_boundary || '--' || UTL_TCP.crlf);
  UTL_SMTP.close_data(l_mail_conn);

  UTL_SMTP.quit(l_mail_conn);
END;
/

内容的提问来源于stack exchange，提问作者VKD