使用Gmail API发送含PDF附件的邮件时遭遇异常

你遇到的问题核心是MIME格式不符合Gmail API的要求，具体两点：

1. PDF、docx这类文件编码成Base64后内容较长，没有按MIME规范每76个字符换行，导致Gmail无法正确解析邮件结构。txt文件体积小，编码后内容短，刚好不会触发这个问题。
2. 最终生成的raw参数使用了标准Base64编码，而Gmail API要求的是URL安全的Base64编码（替换+为-、/为_，移除末尾的=）。

修改代码中的两处关键部分：

1. 给Base64编码的附件内容添加换行 #

新增一个处理函数，确保Base64编码的内容每76字符换一行：

function base64WithLineBreaks(binaryData) {
    var base64Str = binaryEncode(binaryData, "base64");
    var chunked = [];
    for (var i=1; i<=len(base64Str); i+=76) {
        arrayAppend(chunked, mid(base64Str, i, 76));
    }
    return arrayToList(chunked, chr(13)&chr(10));
}

然后在构建mimeMessage时，用这个函数替换原来的binaryEncode调用：

// 替换所有附件的binaryEncode为base64WithLineBreaks
base64WithLineBreaks(attachment1FileContent)
base64WithLineBreaks(attachment2FileContent)
base64WithLineBreaks(attachment3FileContent)

2. 转换为URL安全的Base64编码 #

替换生成rawMessage的代码：

// 原代码：rawMessage = toBase64(mimeText);
// 修改为：
rawMessage = replace(replace(toBase64(mimeText), "+", "-", "all"), "/", "_", "all");
rawMessage = reReplace(rawMessage, "=+$", "", "all");

修改后的关键代码片段 #

// 新增Base64换行处理函数
function base64WithLineBreaks(binaryData) {
    var base64Str = binaryEncode(binaryData, "base64");
    var chunked = [];
    for (var i=1; i<=len(base64Str); i+=76) {
        arrayAppend(chunked, mid(base64Str, i, 76));
    }
    return arrayToList(chunked, chr(13)&chr(10));
}

// ... 其他原有代码不变 ...

// 构建mimeMessage时替换binaryEncode
mimeMessage = [
    "MIME-Version: 1.0",
    "to: " & toEmail,
    "subject: " & subject,
    "Content-Type: multipart/mixed; boundary=" & boundary,
    "",
    "--" & boundary,
    "Content-Type: text/plain; charset=UTF-8",
    "Content-Disposition: inline",
    "",
    bodyText,
    "",
    "--" & boundary,
    "Content-Type: application/octet-stream; name=""" & attachment1FileName & """",
    "Content-Transfer-Encoding: base64",
    "Content-Disposition: attachment; filename=""" & attachment1FileName & """",
    "",
    base64WithLineBreaks(attachment1FileContent),
    "",
    "--" & boundary,
    "Content-Type: application/octet-stream; name=""" & attachment2FileName & """",
    "Content-Transfer-Encoding: base64",
    "Content-Disposition: attachment; filename=""" & attachment2FileName & """",
    "",
    base64WithLineBreaks(attachment2FileContent),
    "",
    "--" & boundary,
    "Content-Type: application/pdf; name=""" & attachment3FileName & """",
    "Content-Transfer-Encoding: base64",
    "Content-Disposition: attachment; filename=""" & attachment3FileName & """",
    "",
    base64WithLineBreaks(attachment3FileContent),
    "--" & boundary & "--"
];

// 生成符合要求的raw参数
mimeText = arrayToList(mimeMessage, chr(13) & chr(10));
rawMessage = replace(replace(toBase64(mimeText), "+", "-", "all"), "/", "_", "all");
rawMessage = reReplace(rawMessage, "=+$", "", "all");

• 换行处理符合RFC 2045规范，确保Gmail能正确解析邮件的MIME结构。
• URL安全的Base64编码是Gmail APIraw参数的强制要求，避免特殊字符导致的请求解析错误。

内容的提问来源于stack exchange，提问作者Hayri ZCAN BRF