为何SMTP的CDO Object无法接受Mail.Sender.SMTPAddress作为.to属性？

我使用Redemption库读取邮件发件人信息，再通过CDO.Object的SMTP协议发送邮件。当通过Mail.Sender.SMTPAddress获取EX类型的发件人邮箱时，会触发以下错误：

CDO.Message.1: The transport lost its connection to the server.

关键现象：

• 当mailReceiver参数来自Redemption的Mail.Sender.SMTPAddress（即使通过cStr()转换为字符串）时，必现错误
• 直接给mailReceiver赋值为相同邮箱的字符串（例如mailReceiver = "xx@like.com"），发送完全正常

以下是我的代码片段：

sub sendMailSMTP(mailSubject, mailSender, mailReceiver, CC, BCC, replyTo, HTMLBody, attachmentsPath_List, REMOTE_SMTP, SMTP, PORT_SMTP, SCHEMAS)
    HTML_CID = ""
    set CDOObject = CreateObject("CDO.Message")
    with CDOObject
        .subject = mailSubject
        .from = mailSender
        .to = mailReceiver
        .CC = CC
        .BCC = BCC
        .replyTo = replyTo
        .HTMLBody = HTMLBody & HTML_CID
        .TextBodyPart.Charset = "utf-8"
        .AddAttachment LOGO_MAIL
        .Attachments(1).Fields.Item("urn:schemas:mailheader:content-disposition") ="attachment;filename="& replace(split(LOGO_MAIL, "\")(ubound(split(LOGO_MAIL, "\"))),".jpg","")
        .Attachments(1).Fields.Update
        for each attachmentPath in attachmentsPath_List
            .AddAttachment attachmentPath
        next
    end with

    with CDOObject.Configuration.Fields
        .Item(SCHEMAS & "sendusing") = REMOTE_SMTP
        .Item(SCHEMAS & "smtpserver") = SMTP
        .Item(SCHEMAS & "smtpserverport") = PORT_SMTP 
        .Item(SCHEMAS & "smtpconnectiontimeout") = 60
        .Update
    end with 
    CDOObject.Send
    set CDOObject = Nothing
end sub 

可能的原因及解决办法 #

• 隐藏不可见字符：Redemption返回的SMTPAddress可能包含零宽空格、换行符这类不可见控制字符，表面和手动输入的字符串一致，但CDO解析时会判定为无效邮箱格式，进而导致SMTP连接异常。
• EX地址格式残留：EX类型是Exchange专属地址格式，Redemption的SMTPAddress虽然返回了SMTP格式字符串，但可能附带Exchange相关的隐藏元数据，转字符串时这些数据没被完全清除，CDO无法正确解析。
• 编码不兼容：Redemption返回的字符串编码和VBScript默认编码不匹配，导致CDO读取到乱码或无效的邮箱内容。

验证与修复步骤 #

1. 检查字符串差异：添加Debug代码对比Redemption获取的地址和手动输入的地址：

   Dim redemptionAddr : redemptionAddr = cStr(Mail.Sender.SMTPAddress)
   Dim manualAddr : manualAddr = "xx@like.com"
   WScript.Echo "Redemption地址长度：" & Len(redemptionAddr) & "，内容：" & redemptionAddr
   WScript.Echo "手动输入地址长度：" & Len(manualAddr) & "，内容：" & manualAddr
   

   如果长度不一致，说明存在隐藏字符。

2. 清理字符串内容：用正则表达式过滤掉所有非打印字符：

   Dim regEx : Set regEx = New RegExp
   regEx.Pattern = "[^\x20-\x7E]" ' 仅保留可打印ASCII字符
   regEx.Global = True
   mailReceiver = regEx.Replace(cStr(Mail.Sender.SMTPAddress), "")
   

3. 直接获取纯SMTP地址：改用Redemption的GetExchangeUser.PrimarySmtpAddress属性获取地址，这个属性会直接返回无残留的纯SMTP格式字符串：

   mailReceiver = Mail.Sender.AddressEntry.GetExchangeUser.PrimarySmtpAddress
   

内容的提问来源于stack exchange，提问作者Nik Ohler