你的问题核心在于错误地对整个mailto:协议链接做了URL编码，导致邮件客户端无法识别这是一个合法的mailto请求——编码后的链接会变成类似mailto%3A%3Fsubject%3D...的格式，完全破坏了mailto协议的结构。

修正步骤： #

1. 仅对subject和body的内容部分单独编码，保留mailto:?subject=&body=这个基础结构不编码
2. 确保Velocity模板中href属性值的语法正确，避免解析异常
3. 统一处理换行符，保证邮件内容在客户端能正常换行

修正后的Java代码 #

// 先拆分主题和邮件内容，分别处理
String rejectSubject = "Rejected - PP - Claim record #20170085";
String rejectBodyContent = "Dear <User name>,\r\n"
        + "Your PP – Claim Record #20170085 request has been Rejected.\r\n"
        + "This is an automated email. Please do not reply.";

String approvedSubject = "Approved - PP - Claim record #20170085";
String approvedBodyContent = "Dear <User name>,\r\n"
        + "Your PP – Claim Record #20170085 request has been Approved.\r\n"
        + "This is an automated email. Please do not reply.";

try {
    // 仅编码主题和内容的可变部分
    String encodedRejectSubject = URLEncoder.encode(rejectSubject, "UTF-8");
    String encodedRejectBody = URLEncoder.encode(rejectBodyContent, "UTF-8");
    // 拼接成完整的合法mailto链接
    String rejectMailto = "mailto:?subject=" + encodedRejectSubject + "&body=" + encodedRejectBody;

    String encodedApprovedSubject = URLEncoder.encode(approvedSubject, "UTF-8");
    String encodedApprovedBody = URLEncoder.encode(approvedBodyContent, "UTF-8");
    String approvedMailto = "mailto:?subject=" + encodedApprovedSubject + "&body=" + encodedApprovedBody;

    claimDetails.setApprovedBody(approvedMailto);
    claimDetails.setRejectBody(rejectMailto);
} catch (UnsupportedEncodingException e) {
    e.printStackTrace();
}

修正后的Velocity模板 #

<div>
    <table align="center" cellspacing="40">
        <th style="background-color: #4CAF50;border-color: #4CAF50;border: 2px solid #4CAF50;padding: 10px 25px 10px 25px;text-align: center;border-radius:5px;">
            <a style="display: block;color: #ffffff;font-size: 15px;text-decoration: none;" href="${email.rejectBody}">
                Reject
            </a>
        </th>
        <th style="background-color: #4CAF50;border-color: #4CAF50;border: 2px solid #4CAF50;padding: 10px 25px 10px 25px;text-align: center;border-radius:5px;">
            <a style="display: block;color: #ffffff;font-size: 15px;text-decoration: none;" href="${email.approvedBody}">
                Approve
            </a>
        </th>
    </table>
</div>

关键说明 #

• 为什么原代码失效：URLEncoder.encode()会把:、?、&这些mailto协议的核心分隔符编码成%3A、%3F、%26，导致整个链接不再被识别为mailto协议请求
• 换行符用\r\n是为了兼容不同邮件客户端，编码后会转为%0D%0A，确保内容换行正常显示
• Velocity模板中href的引号可以避免链接含特殊字符时被错误截断，提升解析稳定性

内容的提问来源于stack exchange，提问作者bharathi